java.nio.file.Files Maven / Gradle / Ivy
Show all versions of android-all Show documentation
/*
* Copyright (c) 2007, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package java.nio.file;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.Closeable;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Reader;
import java.io.UncheckedIOException;
import java.io.Writer;
import java.nio.channels.Channels;
import java.nio.channels.FileChannel;
import java.nio.channels.SeekableByteChannel;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CharsetEncoder;
import java.nio.charset.StandardCharsets;
import java.nio.file.attribute.BasicFileAttributeView;
import java.nio.file.attribute.BasicFileAttributes;
import java.nio.file.attribute.DosFileAttributes; // javadoc
import java.nio.file.attribute.FileAttribute;
import java.nio.file.attribute.FileAttributeView;
import java.nio.file.attribute.FileOwnerAttributeView;
import java.nio.file.attribute.FileStoreAttributeView;
import java.nio.file.attribute.FileTime;
import java.nio.file.attribute.PosixFileAttributeView;
import java.nio.file.attribute.PosixFileAttributes;
import java.nio.file.attribute.PosixFilePermission;
import java.nio.file.attribute.UserPrincipal;
import java.nio.file.spi.FileSystemProvider;
import java.nio.file.spi.FileTypeDetector;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.EnumSet;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.ServiceLoader;
import java.util.Set;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.function.BiPredicate;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
/**
* This class consists exclusively of static methods that operate on files,
* directories, or other types of files.
*
* In most cases, the methods defined here will delegate to the associated
* file system provider to perform the file operations.
*
* @since 1.7
*/
public final class Files {
private Files() { }
/**
* Returns the {@code FileSystemProvider} to delegate to.
*/
private static FileSystemProvider provider(Path path) {
return path.getFileSystem().provider();
}
/**
* Convert a Closeable to a Runnable by converting checked IOException
* to UncheckedIOException
*/
private static Runnable asUncheckedRunnable(Closeable c) {
return () -> {
try {
c.close();
} catch (IOException e) {
throw new UncheckedIOException(e);
}
};
}
// -- File contents --
/**
* Opens a file, returning an input stream to read from the file. The stream
* will not be buffered, and is not required to support the {@link
* InputStream#mark mark} or {@link InputStream#reset reset} methods. The
* stream will be safe for access by multiple concurrent threads. Reading
* commences at the beginning of the file. Whether the returned stream is
* asynchronously closeable and/or interruptible is highly
* file system provider specific and therefore not specified.
*
*
The {@code options} parameter determines how the file is opened.
* If no options are present then it is equivalent to opening the file with
* the {@link StandardOpenOption#READ READ} option. In addition to the {@code
* READ} option, an implementation may also support additional implementation
* specific options.
*
* @param path
* the path to the file to open
* @param options
* options specifying how the file is opened
*
* @return a new input stream
*
* @throws IllegalArgumentException
* if an invalid combination of options is specified
* @throws UnsupportedOperationException
* if an unsupported option is specified
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkRead(String) checkRead}
* method is invoked to check read access to the file.
*/
public static InputStream newInputStream(Path path, OpenOption... options)
throws IOException
{
return provider(path).newInputStream(path, options);
}
/**
* Opens or creates a file, returning an output stream that may be used to
* write bytes to the file. The resulting stream will not be buffered. The
* stream will be safe for access by multiple concurrent threads. Whether
* the returned stream is asynchronously closeable and/or
* interruptible is highly file system provider specific and
* therefore not specified.
*
*
This method opens or creates a file in exactly the manner specified
* by the {@link #newByteChannel(Path,Set,FileAttribute[]) newByteChannel}
* method with the exception that the {@link StandardOpenOption#READ READ}
* option may not be present in the array of options. If no options are
* present then this method works as if the {@link StandardOpenOption#CREATE
* CREATE}, {@link StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING},
* and {@link StandardOpenOption#WRITE WRITE} options are present. In other
* words, it opens the file for writing, creating the file if it doesn't
* exist, or initially truncating an existing {@link #isRegularFile
* regular-file} to a size of {@code 0} if it exists.
*
*
Usage Examples:
*
* Path path = ...
*
* // truncate and overwrite an existing file, or create the file if
* // it doesn't initially exist
* OutputStream out = Files.newOutputStream(path);
*
* // append to an existing file, fail if the file does not exist
* out = Files.newOutputStream(path, APPEND);
*
* // append to an existing file, create file if it doesn't initially exist
* out = Files.newOutputStream(path, CREATE, APPEND);
*
* // always create new file, failing if it already exists
* out = Files.newOutputStream(path, CREATE_NEW);
*
*
* @param path
* the path to the file to open or create
* @param options
* options specifying how the file is opened
*
* @return a new output stream
*
* @throws IllegalArgumentException
* if {@code options} contains an invalid combination of options
* @throws UnsupportedOperationException
* if an unsupported option is specified
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkWrite(String) checkWrite}
* method is invoked to check write access to the file. The {@link
* SecurityManager#checkDelete(String) checkDelete} method is
* invoked to check delete access if the file is opened with the
* {@code DELETE_ON_CLOSE} option.
*/
public static OutputStream newOutputStream(Path path, OpenOption... options)
throws IOException
{
return provider(path).newOutputStream(path, options);
}
/**
* Opens or creates a file, returning a seekable byte channel to access the
* file.
*
* The {@code options} parameter determines how the file is opened.
* The {@link StandardOpenOption#READ READ} and {@link
* StandardOpenOption#WRITE WRITE} options determine if the file should be
* opened for reading and/or writing. If neither option (or the {@link
* StandardOpenOption#APPEND APPEND} option) is present then the file is
* opened for reading. By default reading or writing commence at the
* beginning of the file.
*
*
In the addition to {@code READ} and {@code WRITE}, the following
* options may be present:
*
*
* Option Description
*
* {@link StandardOpenOption#APPEND APPEND}
* If this option is present then the file is opened for writing and
* each invocation of the channel's {@code write} method first advances
* the position to the end of the file and then writes the requested
* data. Whether the advancement of the position and the writing of the
* data are done in a single atomic operation is system-dependent and
* therefore unspecified. This option may not be used in conjunction
* with the {@code READ} or {@code TRUNCATE_EXISTING} options.
*
*
* {@link StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}
* If this option is present then the existing file is truncated to
* a size of 0 bytes. This option is ignored when the file is opened only
* for reading.
*
*
* {@link StandardOpenOption#CREATE_NEW CREATE_NEW}
* If this option is present then a new file is created, failing if
* the file already exists or is a symbolic link. When creating a file the
* check for the existence of the file and the creation of the file if it
* does not exist is atomic with respect to other file system operations.
* This option is ignored when the file is opened only for reading.
*
*
* {@link StandardOpenOption#CREATE CREATE}
* If this option is present then an existing file is opened if it
* exists, otherwise a new file is created. This option is ignored if the
* {@code CREATE_NEW} option is also present or the file is opened only
* for reading.
*
*
* {@link StandardOpenOption#DELETE_ON_CLOSE DELETE_ON_CLOSE}
* When this option is present then the implementation makes a
* best effort attempt to delete the file when closed by the
* {@link SeekableByteChannel#close close} method. If the {@code close}
* method is not invoked then a best effort attempt is made to
* delete the file when the Java virtual machine terminates.
*
*
* {@link StandardOpenOption#SPARSE SPARSE}
* When creating a new file this option is a hint that the
* new file will be sparse. This option is ignored when not creating
* a new file.
*
*
* {@link StandardOpenOption#SYNC SYNC}
* Requires that every update to the file's content or metadata be
* written synchronously to the underlying storage device. (see Synchronized I/O file
* integrity).
*
*
* {@link StandardOpenOption#DSYNC DSYNC}
* Requires that every update to the file's content be written
* synchronously to the underlying storage device. (see Synchronized I/O file
* integrity).
*
*
*
* An implementation may also support additional implementation specific
* options.
*
*
The {@code attrs} parameter is optional {@link FileAttribute
* file-attributes} to set atomically when a new file is created.
*
*
In the case of the default provider, the returned seekable byte channel
* is a {@link java.nio.channels.FileChannel}.
*
*
Usage Examples:
*
* Path path = ...
*
* // open file for reading
* ReadableByteChannel rbc = Files.newByteChannel(path, EnumSet.of(READ)));
*
* // open file for writing to the end of an existing file, creating
* // the file if it doesn't already exist
* WritableByteChannel wbc = Files.newByteChannel(path, EnumSet.of(CREATE,APPEND));
*
* // create file with initial permissions, opening it for both reading and writing
* {@code FileAttribute> perms = ...}
* SeekableByteChannel sbc = Files.newByteChannel(path, EnumSet.of(CREATE_NEW,READ,WRITE), perms);
*
*
* @param path
* the path to the file to open or create
* @param options
* options specifying how the file is opened
* @param attrs
* an optional list of file attributes to set atomically when
* creating the file
*
* @return a new seekable byte channel
*
* @throws IllegalArgumentException
* if the set contains an invalid combination of options
* @throws UnsupportedOperationException
* if an unsupported open option is specified or the array contains
* attributes that cannot be set atomically when creating the file
* @throws FileAlreadyExistsException
* if a file of that name already exists and the {@link
* StandardOpenOption#CREATE_NEW CREATE_NEW} option is specified
* (optional specific exception)
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkRead(String) checkRead}
* method is invoked to check read access to the path if the file is
* opened for reading. The {@link SecurityManager#checkWrite(String)
* checkWrite} method is invoked to check write access to the path
* if the file is opened for writing. The {@link
* SecurityManager#checkDelete(String) checkDelete} method is
* invoked to check delete access if the file is opened with the
* {@code DELETE_ON_CLOSE} option.
*
* @see java.nio.channels.FileChannel#open(Path,Set,FileAttribute[])
*/
public static SeekableByteChannel newByteChannel(Path path,
Set options,
FileAttribute... attrs)
throws IOException
{
return provider(path).newByteChannel(path, options, attrs);
}
/**
* Opens or creates a file, returning a seekable byte channel to access the
* file.
*
* This method opens or creates a file in exactly the manner specified
* by the {@link #newByteChannel(Path,Set,FileAttribute[]) newByteChannel}
* method.
*
* @param path
* the path to the file to open or create
* @param options
* options specifying how the file is opened
*
* @return a new seekable byte channel
*
* @throws IllegalArgumentException
* if the set contains an invalid combination of options
* @throws UnsupportedOperationException
* if an unsupported open option is specified
* @throws FileAlreadyExistsException
* if a file of that name already exists and the {@link
* StandardOpenOption#CREATE_NEW CREATE_NEW} option is specified
* (optional specific exception)
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkRead(String) checkRead}
* method is invoked to check read access to the path if the file is
* opened for reading. The {@link SecurityManager#checkWrite(String)
* checkWrite} method is invoked to check write access to the path
* if the file is opened for writing. The {@link
* SecurityManager#checkDelete(String) checkDelete} method is
* invoked to check delete access if the file is opened with the
* {@code DELETE_ON_CLOSE} option.
*
* @see java.nio.channels.FileChannel#open(Path,OpenOption[])
*/
public static SeekableByteChannel newByteChannel(Path path, OpenOption... options)
throws IOException
{
Set set = new HashSet(options.length);
Collections.addAll(set, options);
return newByteChannel(path, set);
}
// -- Directories --
private static class AcceptAllFilter
implements DirectoryStream.Filter
{
private AcceptAllFilter() { }
@Override
public boolean accept(Path entry) { return true; }
static final AcceptAllFilter FILTER = new AcceptAllFilter();
}
/**
* Opens a directory, returning a {@link DirectoryStream} to iterate over
* all entries in the directory. The elements returned by the directory
* stream's {@link DirectoryStream#iterator iterator} are of type {@code
* Path}, each one representing an entry in the directory. The {@code Path}
* objects are obtained as if by {@link Path#resolve(Path) resolving} the
* name of the directory entry against {@code dir}.
*
* When not using the try-with-resources construct, then directory
* stream's {@code close} method should be invoked after iteration is
* completed so as to free any resources held for the open directory.
*
*
When an implementation supports operations on entries in the
* directory that execute in a race-free manner then the returned directory
* stream is a {@link SecureDirectoryStream}.
*
* @param dir
* the path to the directory
*
* @return a new and open {@code DirectoryStream} object
*
* @throws NotDirectoryException
* if the file could not otherwise be opened because it is not
* a directory (optional specific exception)
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkRead(String) checkRead}
* method is invoked to check read access to the directory.
*/
public static DirectoryStream newDirectoryStream(Path dir)
throws IOException
{
return provider(dir).newDirectoryStream(dir, AcceptAllFilter.FILTER);
}
/**
* Opens a directory, returning a {@link DirectoryStream} to iterate over
* the entries in the directory. The elements returned by the directory
* stream's {@link DirectoryStream#iterator iterator} are of type {@code
* Path}, each one representing an entry in the directory. The {@code Path}
* objects are obtained as if by {@link Path#resolve(Path) resolving} the
* name of the directory entry against {@code dir}. The entries returned by
* the iterator are filtered by matching the {@code String} representation
* of their file names against the given globbing pattern.
*
* For example, suppose we want to iterate over the files ending with
* ".java" in a directory:
*
* Path dir = ...
* try (DirectoryStream<Path> stream = Files.newDirectoryStream(dir, "*.java")) {
* :
* }
*
*
* The globbing pattern is specified by the {@link
* FileSystem#getPathMatcher getPathMatcher} method.
*
*
When not using the try-with-resources construct, then directory
* stream's {@code close} method should be invoked after iteration is
* completed so as to free any resources held for the open directory.
*
*
When an implementation supports operations on entries in the
* directory that execute in a race-free manner then the returned directory
* stream is a {@link SecureDirectoryStream}.
*
* @param dir
* the path to the directory
* @param glob
* the glob pattern
*
* @return a new and open {@code DirectoryStream} object
*
* @throws java.util.regex.PatternSyntaxException
* if the pattern is invalid
* @throws NotDirectoryException
* if the file could not otherwise be opened because it is not
* a directory (optional specific exception)
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkRead(String) checkRead}
* method is invoked to check read access to the directory.
*/
public static DirectoryStream newDirectoryStream(Path dir, String glob)
throws IOException
{
// avoid creating a matcher if all entries are required.
if (glob.equals("*"))
return newDirectoryStream(dir);
// create a matcher and return a filter that uses it.
FileSystem fs = dir.getFileSystem();
final PathMatcher matcher = fs.getPathMatcher("glob:" + glob);
DirectoryStream.Filter filter = new DirectoryStream.Filter() {
@Override
public boolean accept(Path entry) {
return matcher.matches(entry.getFileName());
}
};
return fs.provider().newDirectoryStream(dir, filter);
}
/**
* Opens a directory, returning a {@link DirectoryStream} to iterate over
* the entries in the directory. The elements returned by the directory
* stream's {@link DirectoryStream#iterator iterator} are of type {@code
* Path}, each one representing an entry in the directory. The {@code Path}
* objects are obtained as if by {@link Path#resolve(Path) resolving} the
* name of the directory entry against {@code dir}. The entries returned by
* the iterator are filtered by the given {@link DirectoryStream.Filter
* filter}.
*
* When not using the try-with-resources construct, then directory
* stream's {@code close} method should be invoked after iteration is
* completed so as to free any resources held for the open directory.
*
*
Where the filter terminates due to an uncaught error or runtime
* exception then it is propagated to the {@link Iterator#hasNext()
* hasNext} or {@link Iterator#next() next} method. Where an {@code
* IOException} is thrown, it results in the {@code hasNext} or {@code
* next} method throwing a {@link DirectoryIteratorException} with the
* {@code IOException} as the cause.
*
*
When an implementation supports operations on entries in the
* directory that execute in a race-free manner then the returned directory
* stream is a {@link SecureDirectoryStream}.
*
*
Usage Example:
* Suppose we want to iterate over the files in a directory that are
* larger than 8K.
*
* DirectoryStream.Filter<Path> filter = new DirectoryStream.Filter<Path>() {
* public boolean accept(Path file) throws IOException {
* return (Files.size(file) > 8192L);
* }
* };
* Path dir = ...
* try (DirectoryStream<Path> stream = Files.newDirectoryStream(dir, filter)) {
* :
* }
*
*
* @param dir
* the path to the directory
* @param filter
* the directory stream filter
*
* @return a new and open {@code DirectoryStream} object
*
* @throws NotDirectoryException
* if the file could not otherwise be opened because it is not
* a directory (optional specific exception)
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkRead(String) checkRead}
* method is invoked to check read access to the directory.
*/
public static DirectoryStream newDirectoryStream(Path dir,
DirectoryStream.Filter filter)
throws IOException
{
return provider(dir).newDirectoryStream(dir, filter);
}
// -- Creation and deletion --
/**
* Creates a new and empty file, failing if the file already exists. The
* check for the existence of the file and the creation of the new file if
* it does not exist are a single operation that is atomic with respect to
* all other filesystem activities that might affect the directory.
*
* The {@code attrs} parameter is optional {@link FileAttribute
* file-attributes} to set atomically when creating the file. Each attribute
* is identified by its {@link FileAttribute#name name}. If more than one
* attribute of the same name is included in the array then all but the last
* occurrence is ignored.
*
* @param path
* the path to the file to create
* @param attrs
* an optional list of file attributes to set atomically when
* creating the file
*
* @return the file
*
* @throws UnsupportedOperationException
* if the array contains an attribute that cannot be set atomically
* when creating the file
* @throws FileAlreadyExistsException
* if a file of that name already exists
* (optional specific exception)
* @throws IOException
* if an I/O error occurs or the parent directory does not exist
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkWrite(String) checkWrite}
* method is invoked to check write access to the new file.
*/
public static Path createFile(Path path, FileAttribute... attrs)
throws IOException
{
EnumSet options =
EnumSet.of(StandardOpenOption.CREATE_NEW, StandardOpenOption.WRITE);
newByteChannel(path, options, attrs).close();
return path;
}
/**
* Creates a new directory. The check for the existence of the file and the
* creation of the directory if it does not exist are a single operation
* that is atomic with respect to all other filesystem activities that might
* affect the directory. The {@link #createDirectories createDirectories}
* method should be used where it is required to create all nonexistent
* parent directories first.
*
* The {@code attrs} parameter is optional {@link FileAttribute
* file-attributes} to set atomically when creating the directory. Each
* attribute is identified by its {@link FileAttribute#name name}. If more
* than one attribute of the same name is included in the array then all but
* the last occurrence is ignored.
*
* @param dir
* the directory to create
* @param attrs
* an optional list of file attributes to set atomically when
* creating the directory
*
* @return the directory
*
* @throws UnsupportedOperationException
* if the array contains an attribute that cannot be set atomically
* when creating the directory
* @throws FileAlreadyExistsException
* if a directory could not otherwise be created because a file of
* that name already exists (optional specific exception)
* @throws IOException
* if an I/O error occurs or the parent directory does not exist
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkWrite(String) checkWrite}
* method is invoked to check write access to the new directory.
*/
public static Path createDirectory(Path dir, FileAttribute... attrs)
throws IOException
{
provider(dir).createDirectory(dir, attrs);
return dir;
}
/**
* Creates a directory by creating all nonexistent parent directories first.
* Unlike the {@link #createDirectory createDirectory} method, an exception
* is not thrown if the directory could not be created because it already
* exists.
*
*
The {@code attrs} parameter is optional {@link FileAttribute
* file-attributes} to set atomically when creating the nonexistent
* directories. Each file attribute is identified by its {@link
* FileAttribute#name name}. If more than one attribute of the same name is
* included in the array then all but the last occurrence is ignored.
*
*
If this method fails, then it may do so after creating some, but not
* all, of the parent directories.
*
* @param dir
* the directory to create
*
* @param attrs
* an optional list of file attributes to set atomically when
* creating the directory
*
* @return the directory
*
* @throws UnsupportedOperationException
* if the array contains an attribute that cannot be set atomically
* when creating the directory
* @throws FileAlreadyExistsException
* if {@code dir} exists but is not a directory (optional specific
* exception)
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* in the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkWrite(String) checkWrite}
* method is invoked prior to attempting to create a directory and
* its {@link SecurityManager#checkRead(String) checkRead} is
* invoked for each parent directory that is checked. If {@code
* dir} is not an absolute path then its {@link Path#toAbsolutePath
* toAbsolutePath} may need to be invoked to get its absolute path.
* This may invoke the security manager's {@link
* SecurityManager#checkPropertyAccess(String) checkPropertyAccess}
* method to check access to the system property {@code user.dir}
*/
public static Path createDirectories(Path dir, FileAttribute... attrs)
throws IOException
{
// attempt to create the directory
try {
createAndCheckIsDirectory(dir, attrs);
return dir;
} catch (FileAlreadyExistsException x) {
// file exists and is not a directory
throw x;
} catch (IOException x) {
// parent may not exist or other reason
}
SecurityException se = null;
try {
dir = dir.toAbsolutePath();
} catch (SecurityException x) {
// don't have permission to get absolute path
se = x;
}
// find a decendent that exists
Path parent = dir.getParent();
while (parent != null) {
try {
provider(parent).checkAccess(parent);
break;
} catch (NoSuchFileException x) {
// does not exist
}
parent = parent.getParent();
}
if (parent == null) {
// unable to find existing parent
if (se == null) {
throw new FileSystemException(dir.toString(), null,
"Unable to determine if root directory exists");
} else {
throw se;
}
}
// create directories
Path child = parent;
for (Path name: parent.relativize(dir)) {
child = child.resolve(name);
createAndCheckIsDirectory(child, attrs);
}
return dir;
}
/**
* Used by createDirectories to attempt to create a directory. A no-op
* if the directory already exists.
*/
private static void createAndCheckIsDirectory(Path dir,
FileAttribute... attrs)
throws IOException
{
try {
createDirectory(dir, attrs);
} catch (FileAlreadyExistsException x) {
if (!isDirectory(dir, LinkOption.NOFOLLOW_LINKS))
throw x;
}
}
/**
* Creates a new empty file in the specified directory, using the given
* prefix and suffix strings to generate its name. The resulting
* {@code Path} is associated with the same {@code FileSystem} as the given
* directory.
*
*
The details as to how the name of the file is constructed is
* implementation dependent and therefore not specified. Where possible
* the {@code prefix} and {@code suffix} are used to construct candidate
* names in the same manner as the {@link
* java.io.File#createTempFile(String,String,File)} method.
*
*
As with the {@code File.createTempFile} methods, this method is only
* part of a temporary-file facility. Where used as a work files,
* the resulting file may be opened using the {@link
* StandardOpenOption#DELETE_ON_CLOSE DELETE_ON_CLOSE} option so that the
* file is deleted when the appropriate {@code close} method is invoked.
* Alternatively, a {@link Runtime#addShutdownHook shutdown-hook}, or the
* {@link java.io.File#deleteOnExit} mechanism may be used to delete the
* file automatically.
*
*
The {@code attrs} parameter is optional {@link FileAttribute
* file-attributes} to set atomically when creating the file. Each attribute
* is identified by its {@link FileAttribute#name name}. If more than one
* attribute of the same name is included in the array then all but the last
* occurrence is ignored. When no file attributes are specified, then the
* resulting file may have more restrictive access permissions to files
* created by the {@link java.io.File#createTempFile(String,String,File)}
* method.
*
* @param dir
* the path to directory in which to create the file
* @param prefix
* the prefix string to be used in generating the file's name;
* may be {@code null}
* @param suffix
* the suffix string to be used in generating the file's name;
* may be {@code null}, in which case "{@code .tmp}" is used
* @param attrs
* an optional list of file attributes to set atomically when
* creating the file
*
* @return the path to the newly created file that did not exist before
* this method was invoked
*
* @throws IllegalArgumentException
* if the prefix or suffix parameters cannot be used to generate
* a candidate file name
* @throws UnsupportedOperationException
* if the array contains an attribute that cannot be set atomically
* when creating the directory
* @throws IOException
* if an I/O error occurs or {@code dir} does not exist
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkWrite(String) checkWrite}
* method is invoked to check write access to the file.
*/
public static Path createTempFile(Path dir,
String prefix,
String suffix,
FileAttribute... attrs)
throws IOException
{
return TempFileHelper.createTempFile(Objects.requireNonNull(dir),
prefix, suffix, attrs);
}
/**
* Creates an empty file in the default temporary-file directory, using
* the given prefix and suffix to generate its name. The resulting {@code
* Path} is associated with the default {@code FileSystem}.
*
*
This method works in exactly the manner specified by the
* {@link #createTempFile(Path,String,String,FileAttribute[])} method for
* the case that the {@code dir} parameter is the temporary-file directory.
*
* @param prefix
* the prefix string to be used in generating the file's name;
* may be {@code null}
* @param suffix
* the suffix string to be used in generating the file's name;
* may be {@code null}, in which case "{@code .tmp}" is used
* @param attrs
* an optional list of file attributes to set atomically when
* creating the file
*
* @return the path to the newly created file that did not exist before
* this method was invoked
*
* @throws IllegalArgumentException
* if the prefix or suffix parameters cannot be used to generate
* a candidate file name
* @throws UnsupportedOperationException
* if the array contains an attribute that cannot be set atomically
* when creating the directory
* @throws IOException
* if an I/O error occurs or the temporary-file directory does not
* exist
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkWrite(String) checkWrite}
* method is invoked to check write access to the file.
*/
public static Path createTempFile(String prefix,
String suffix,
FileAttribute... attrs)
throws IOException
{
return TempFileHelper.createTempFile(null, prefix, suffix, attrs);
}
/**
* Creates a new directory in the specified directory, using the given
* prefix to generate its name. The resulting {@code Path} is associated
* with the same {@code FileSystem} as the given directory.
*
*
The details as to how the name of the directory is constructed is
* implementation dependent and therefore not specified. Where possible
* the {@code prefix} is used to construct candidate names.
*
*
As with the {@code createTempFile} methods, this method is only
* part of a temporary-file facility. A {@link Runtime#addShutdownHook
* shutdown-hook}, or the {@link java.io.File#deleteOnExit} mechanism may be
* used to delete the directory automatically.
*
*
The {@code attrs} parameter is optional {@link FileAttribute
* file-attributes} to set atomically when creating the directory. Each
* attribute is identified by its {@link FileAttribute#name name}. If more
* than one attribute of the same name is included in the array then all but
* the last occurrence is ignored.
*
* @param dir
* the path to directory in which to create the directory
* @param prefix
* the prefix string to be used in generating the directory's name;
* may be {@code null}
* @param attrs
* an optional list of file attributes to set atomically when
* creating the directory
*
* @return the path to the newly created directory that did not exist before
* this method was invoked
*
* @throws IllegalArgumentException
* if the prefix cannot be used to generate a candidate directory name
* @throws UnsupportedOperationException
* if the array contains an attribute that cannot be set atomically
* when creating the directory
* @throws IOException
* if an I/O error occurs or {@code dir} does not exist
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkWrite(String) checkWrite}
* method is invoked to check write access when creating the
* directory.
*/
public static Path createTempDirectory(Path dir,
String prefix,
FileAttribute... attrs)
throws IOException
{
return TempFileHelper.createTempDirectory(Objects.requireNonNull(dir),
prefix, attrs);
}
/**
* Creates a new directory in the default temporary-file directory, using
* the given prefix to generate its name. The resulting {@code Path} is
* associated with the default {@code FileSystem}.
*
*
This method works in exactly the manner specified by {@link
* #createTempDirectory(Path,String,FileAttribute[])} method for the case
* that the {@code dir} parameter is the temporary-file directory.
*
* @param prefix
* the prefix string to be used in generating the directory's name;
* may be {@code null}
* @param attrs
* an optional list of file attributes to set atomically when
* creating the directory
*
* @return the path to the newly created directory that did not exist before
* this method was invoked
*
* @throws IllegalArgumentException
* if the prefix cannot be used to generate a candidate directory name
* @throws UnsupportedOperationException
* if the array contains an attribute that cannot be set atomically
* when creating the directory
* @throws IOException
* if an I/O error occurs or the temporary-file directory does not
* exist
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkWrite(String) checkWrite}
* method is invoked to check write access when creating the
* directory.
*/
public static Path createTempDirectory(String prefix,
FileAttribute... attrs)
throws IOException
{
return TempFileHelper.createTempDirectory(null, prefix, attrs);
}
/**
* Creates a symbolic link to a target (optional operation).
*
*
The {@code target} parameter is the target of the link. It may be an
* {@link Path#isAbsolute absolute} or relative path and may not exist. When
* the target is a relative path then file system operations on the resulting
* link are relative to the path of the link.
*
*
The {@code attrs} parameter is optional {@link FileAttribute
* attributes} to set atomically when creating the link. Each attribute is
* identified by its {@link FileAttribute#name name}. If more than one attribute
* of the same name is included in the array then all but the last occurrence
* is ignored.
*
*
Where symbolic links are supported, but the underlying {@link FileStore}
* does not support symbolic links, then this may fail with an {@link
* IOException}. Additionally, some operating systems may require that the
* Java virtual machine be started with implementation specific privileges to
* create symbolic links, in which case this method may throw {@code IOException}.
*
* @param link
* the path of the symbolic link to create
* @param target
* the target of the symbolic link
* @param attrs
* the array of attributes to set atomically when creating the
* symbolic link
*
* @return the path to the symbolic link
*
* @throws UnsupportedOperationException
* if the implementation does not support symbolic links or the
* array contains an attribute that cannot be set atomically when
* creating the symbolic link
* @throws FileAlreadyExistsException
* if a file with the name already exists (optional specific
* exception)
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, and a security manager
* is installed, it denies {@link LinkPermission}("symbolic")
* or its {@link SecurityManager#checkWrite(String) checkWrite}
* method denies write access to the path of the symbolic link.
*/
public static Path createSymbolicLink(Path link, Path target,
FileAttribute... attrs)
throws IOException
{
provider(link).createSymbolicLink(link, target, attrs);
return link;
}
/**
* Creates a new link (directory entry) for an existing file (optional
* operation).
*
*
The {@code link} parameter locates the directory entry to create.
* The {@code existing} parameter is the path to an existing file. This
* method creates a new directory entry for the file so that it can be
* accessed using {@code link} as the path. On some file systems this is
* known as creating a "hard link". Whether the file attributes are
* maintained for the file or for each directory entry is file system
* specific and therefore not specified. Typically, a file system requires
* that all links (directory entries) for a file be on the same file system.
* Furthermore, on some platforms, the Java virtual machine may require to
* be started with implementation specific privileges to create hard links
* or to create links to directories.
*
* @param link
* the link (directory entry) to create
* @param existing
* a path to an existing file
*
* @return the path to the link (directory entry)
*
* @throws UnsupportedOperationException
* if the implementation does not support adding an existing file
* to a directory
* @throws FileAlreadyExistsException
* if the entry could not otherwise be created because a file of
* that name already exists (optional specific exception)
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, and a security manager
* is installed, it denies {@link LinkPermission}("hard")
* or its {@link SecurityManager#checkWrite(String) checkWrite}
* method denies write access to either the link or the
* existing file.
*/
public static Path createLink(Path link, Path existing) throws IOException {
provider(link).createLink(link, existing);
return link;
}
/**
* Deletes a file.
*
*
An implementation may require to examine the file to determine if the
* file is a directory. Consequently this method may not be atomic with respect
* to other file system operations. If the file is a symbolic link then the
* symbolic link itself, not the final target of the link, is deleted.
*
*
If the file is a directory then the directory must be empty. In some
* implementations a directory has entries for special files or links that
* are created when the directory is created. In such implementations a
* directory is considered empty when only the special entries exist.
* This method can be used with the {@link #walkFileTree walkFileTree}
* method to delete a directory and all entries in the directory, or an
* entire file-tree where required.
*
*
On some operating systems it may not be possible to remove a file when
* it is open and in use by this Java virtual machine or other programs.
*
* @param path
* the path to the file to delete
*
* @throws NoSuchFileException
* if the file does not exist (optional specific exception)
* @throws DirectoryNotEmptyException
* if the file is a directory and could not otherwise be deleted
* because the directory is not empty (optional specific
* exception)
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkDelete(String)} method
* is invoked to check delete access to the file
*/
public static void delete(Path path) throws IOException {
provider(path).delete(path);
}
/**
* Deletes a file if it exists.
*
*
As with the {@link #delete(Path) delete(Path)} method, an
* implementation may need to examine the file to determine if the file is a
* directory. Consequently this method may not be atomic with respect to
* other file system operations. If the file is a symbolic link, then the
* symbolic link itself, not the final target of the link, is deleted.
*
*
If the file is a directory then the directory must be empty. In some
* implementations a directory has entries for special files or links that
* are created when the directory is created. In such implementations a
* directory is considered empty when only the special entries exist.
*
*
On some operating systems it may not be possible to remove a file when
* it is open and in use by this Java virtual machine or other programs.
*
* @param path
* the path to the file to delete
*
* @return {@code true} if the file was deleted by this method; {@code
* false} if the file could not be deleted because it did not
* exist
*
* @throws DirectoryNotEmptyException
* if the file is a directory and could not otherwise be deleted
* because the directory is not empty (optional specific
* exception)
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkDelete(String)} method
* is invoked to check delete access to the file.
*/
public static boolean deleteIfExists(Path path) throws IOException {
return provider(path).deleteIfExists(path);
}
// -- Copying and moving files --
/**
* Copy a file to a target file.
*
*
This method copies a file to the target file with the {@code
* options} parameter specifying how the copy is performed. By default, the
* copy fails if the target file already exists or is a symbolic link,
* except if the source and target are the {@link #isSameFile same} file, in
* which case the method completes without copying the file. File attributes
* are not required to be copied to the target file. If symbolic links are
* supported, and the file is a symbolic link, then the final target of the
* link is copied. If the file is a directory then it creates an empty
* directory in the target location (entries in the directory are not
* copied). This method can be used with the {@link #walkFileTree
* walkFileTree} method to copy a directory and all entries in the directory,
* or an entire file-tree where required.
*
*
The {@code options} parameter may include any of the following:
*
*
* Option Description
*
* {@link StandardCopyOption#REPLACE_EXISTING REPLACE_EXISTING}
* If the target file exists, then the target file is replaced if it
* is not a non-empty directory. If the target file exists and is a
* symbolic link, then the symbolic link itself, not the target of
* the link, is replaced.
*
*
* {@link StandardCopyOption#COPY_ATTRIBUTES COPY_ATTRIBUTES}
* Attempts to copy the file attributes associated with this file to
* the target file. The exact file attributes that are copied is platform
* and file system dependent and therefore unspecified. Minimally, the
* {@link BasicFileAttributes#lastModifiedTime last-modified-time} is
* copied to the target file if supported by both the source and target
* file stores. Copying of file timestamps may result in precision
* loss.
*
*
* {@link LinkOption#NOFOLLOW_LINKS NOFOLLOW_LINKS}
* Symbolic links are not followed. If the file is a symbolic link,
* then the symbolic link itself, not the target of the link, is copied.
* It is implementation specific if file attributes can be copied to the
* new link. In other words, the {@code COPY_ATTRIBUTES} option may be
* ignored when copying a symbolic link.
*
*
*
* An implementation of this interface may support additional
* implementation specific options.
*
*
Copying a file is not an atomic operation. If an {@link IOException}
* is thrown, then it is possible that the target file is incomplete or some
* of its file attributes have not been copied from the source file. When
* the {@code REPLACE_EXISTING} option is specified and the target file
* exists, then the target file is replaced. The check for the existence of
* the file and the creation of the new file may not be atomic with respect
* to other file system activities.
*
*
Usage Example:
* Suppose we want to copy a file into a directory, giving it the same file
* name as the source file:
*
* Path source = ...
* Path newdir = ...
* Files.copy(source, newdir.resolve(source.getFileName());
*
*
* @param source
* the path to the file to copy
* @param target
* the path to the target file (may be associated with a different
* provider to the source path)
* @param options
* options specifying how the copy should be done
*
* @return the path to the target file
*
* @throws UnsupportedOperationException
* if the array contains a copy option that is not supported
* @throws FileAlreadyExistsException
* if the target file exists but cannot be replaced because the
* {@code REPLACE_EXISTING} option is not specified (optional
* specific exception)
* @throws DirectoryNotEmptyException
* the {@code REPLACE_EXISTING} option is specified but the file
* cannot be replaced because it is a non-empty directory
* (optional specific exception)
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkRead(String) checkRead}
* method is invoked to check read access to the source file, the
* {@link SecurityManager#checkWrite(String) checkWrite} is invoked
* to check write access to the target file. If a symbolic link is
* copied the security manager is invoked to check {@link
* LinkPermission}{@code ("symbolic")}.
*/
public static Path copy(Path source, Path target, CopyOption... options)
throws IOException
{
FileSystemProvider provider = provider(source);
if (provider(target) == provider) {
// same provider
provider.copy(source, target, options);
} else {
// different providers
CopyMoveHelper.copyToForeignTarget(source, target, options);
}
return target;
}
/**
* Move or rename a file to a target file.
*
* By default, this method attempts to move the file to the target
* file, failing if the target file exists except if the source and
* target are the {@link #isSameFile same} file, in which case this method
* has no effect. If the file is a symbolic link then the symbolic link
* itself, not the target of the link, is moved. This method may be
* invoked to move an empty directory. In some implementations a directory
* has entries for special files or links that are created when the
* directory is created. In such implementations a directory is considered
* empty when only the special entries exist. When invoked to move a
* directory that is not empty then the directory is moved if it does not
* require moving the entries in the directory. For example, renaming a
* directory on the same {@link FileStore} will usually not require moving
* the entries in the directory. When moving a directory requires that its
* entries be moved then this method fails (by throwing an {@code
* IOException}). To move a file tree may involve copying rather
* than moving directories and this can be done using the {@link
* #copy copy} method in conjunction with the {@link
* #walkFileTree Files.walkFileTree} utility method.
*
*
The {@code options} parameter may include any of the following:
*
*
* Option Description
*
* {@link StandardCopyOption#REPLACE_EXISTING REPLACE_EXISTING}
* If the target file exists, then the target file is replaced if it
* is not a non-empty directory. If the target file exists and is a
* symbolic link, then the symbolic link itself, not the target of
* the link, is replaced.
*
*
* {@link StandardCopyOption#ATOMIC_MOVE ATOMIC_MOVE}
* The move is performed as an atomic file system operation and all
* other options are ignored. If the target file exists then it is
* implementation specific if the existing file is replaced or this method
* fails by throwing an {@link IOException}. If the move cannot be
* performed as an atomic file system operation then {@link
* AtomicMoveNotSupportedException} is thrown. This can arise, for
* example, when the target location is on a different {@code FileStore}
* and would require that the file be copied, or target location is
* associated with a different provider to this object.
*
*
* An implementation of this interface may support additional
* implementation specific options.
*
*
Moving a file will copy the {@link
* BasicFileAttributes#lastModifiedTime last-modified-time} to the target
* file if supported by both source and target file stores. Copying of file
* timestamps may result in precision loss. An implementation may also
* attempt to copy other file attributes but is not required to fail if the
* file attributes cannot be copied. When the move is performed as
* a non-atomic operation, and an {@code IOException} is thrown, then the
* state of the files is not defined. The original file and the target file
* may both exist, the target file may be incomplete or some of its file
* attributes may not been copied from the original file.
*
*
Usage Examples:
* Suppose we want to rename a file to "newname", keeping the file in the
* same directory:
*
* Path source = ...
* Files.move(source, source.resolveSibling("newname"));
*
* Alternatively, suppose we want to move a file to new directory, keeping
* the same file name, and replacing any existing file of that name in the
* directory:
*
* Path source = ...
* Path newdir = ...
* Files.move(source, newdir.resolve(source.getFileName()), REPLACE_EXISTING);
*
*
* @param source
* the path to the file to move
* @param target
* the path to the target file (may be associated with a different
* provider to the source path)
* @param options
* options specifying how the move should be done
*
* @return the path to the target file
*
* @throws UnsupportedOperationException
* if the array contains a copy option that is not supported
* @throws FileAlreadyExistsException
* if the target file exists but cannot be replaced because the
* {@code REPLACE_EXISTING} option is not specified (optional
* specific exception)
* @throws DirectoryNotEmptyException
* the {@code REPLACE_EXISTING} option is specified but the file
* cannot be replaced because it is a non-empty directory
* (optional specific exception)
* @throws AtomicMoveNotSupportedException
* if the options array contains the {@code ATOMIC_MOVE} option but
* the file cannot be moved as an atomic file system operation.
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkWrite(String) checkWrite}
* method is invoked to check write access to both the source and
* target file.
*/
public static Path move(Path source, Path target, CopyOption... options)
throws IOException
{
FileSystemProvider provider = provider(source);
if (provider(target) == provider) {
// same provider
provider.move(source, target, options);
} else {
// different providers
CopyMoveHelper.moveToForeignTarget(source, target, options);
}
return target;
}
// -- Miscellenous --
/**
* Reads the target of a symbolic link (optional operation).
*
* If the file system supports symbolic
* links then this method is used to read the target of the link, failing
* if the file is not a symbolic link. The target of the link need not exist.
* The returned {@code Path} object will be associated with the same file
* system as {@code link}.
*
* @param link
* the path to the symbolic link
*
* @return a {@code Path} object representing the target of the link
*
* @throws UnsupportedOperationException
* if the implementation does not support symbolic links
* @throws NotLinkException
* if the target could otherwise not be read because the file
* is not a symbolic link (optional specific exception)
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, and a security manager
* is installed, it checks that {@code FilePermission} has been
* granted with the "{@code readlink}" action to read the link.
*/
public static Path readSymbolicLink(Path link) throws IOException {
return provider(link).readSymbolicLink(link);
}
/**
* Returns the {@link FileStore} representing the file store where a file
* is located.
*
*
Once a reference to the {@code FileStore} is obtained it is
* implementation specific if operations on the returned {@code FileStore},
* or {@link FileStoreAttributeView} objects obtained from it, continue
* to depend on the existence of the file. In particular the behavior is not
* defined for the case that the file is deleted or moved to a different
* file store.
*
* @param path
* the path to the file
*
* @return the file store where the file is stored
*
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkRead(String) checkRead}
* method is invoked to check read access to the file, and in
* addition it checks {@link RuntimePermission}
* ("getFileStoreAttributes")
*/
public static FileStore getFileStore(Path path) throws IOException {
return provider(path).getFileStore(path);
}
/**
* Tests if two paths locate the same file.
*
*
If both {@code Path} objects are {@link Path#equals(Object) equal}
* then this method returns {@code true} without checking if the file exists.
* If the two {@code Path} objects are associated with different providers
* then this method returns {@code false}. Otherwise, this method checks if
* both {@code Path} objects locate the same file, and depending on the
* implementation, may require to open or access both files.
*
*
If the file system and files remain static, then this method implements
* an equivalence relation for non-null {@code Paths}.
*
* - It is reflexive: for {@code Path} {@code f},
* {@code isSameFile(f,f)} should return {@code true}.
*
- It is symmetric: for two {@code Paths} {@code f} and {@code g},
* {@code isSameFile(f,g)} will equal {@code isSameFile(g,f)}.
*
- It is transitive: for three {@code Paths}
* {@code f}, {@code g}, and {@code h}, if {@code isSameFile(f,g)} returns
* {@code true} and {@code isSameFile(g,h)} returns {@code true}, then
* {@code isSameFile(f,h)} will return return {@code true}.
*
*
* @param path
* one path to the file
* @param path2
* the other path
*
* @return {@code true} if, and only if, the two paths locate the same file
*
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkRead(String) checkRead}
* method is invoked to check read access to both files.
*
* @see java.nio.file.attribute.BasicFileAttributes#fileKey
*/
public static boolean isSameFile(Path path, Path path2) throws IOException {
return provider(path).isSameFile(path, path2);
}
/**
* Tells whether or not a file is considered hidden. The exact
* definition of hidden is platform or provider dependent. On UNIX for
* example a file is considered to be hidden if its name begins with a
* period character ('.'). On Windows a file is considered hidden if it
* isn't a directory and the DOS {@link DosFileAttributes#isHidden hidden}
* attribute is set.
*
* Depending on the implementation this method may require to access
* the file system to determine if the file is considered hidden.
*
* @param path
* the path to the file to test
*
* @return {@code true} if the file is considered hidden
*
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkRead(String) checkRead}
* method is invoked to check read access to the file.
*/
public static boolean isHidden(Path path) throws IOException {
return provider(path).isHidden(path);
}
// lazy loading of default and installed file type detectors
private static class FileTypeDetectors{
static final FileTypeDetector defaultFileTypeDetector =
createDefaultFileTypeDetector();
static final List installeDetectors =
loadInstalledDetectors();
// creates the default file type detector
private static FileTypeDetector createDefaultFileTypeDetector() {
return AccessController
.doPrivileged(new PrivilegedAction() {
@Override public FileTypeDetector run() {
return sun.nio.fs.DefaultFileTypeDetector.create();
}});
}
// loads all installed file type detectors
private static List loadInstalledDetectors() {
return AccessController
.doPrivileged(new PrivilegedAction>() {
@Override public List run() {
List list = new ArrayList<>();
ServiceLoader loader = ServiceLoader
.load(FileTypeDetector.class, ClassLoader.getSystemClassLoader());
for (FileTypeDetector detector: loader) {
list.add(detector);
}
return list;
}});
}
}
/**
* Probes the content type of a file.
*
* This method uses the installed {@link FileTypeDetector} implementations
* to probe the given file to determine its content type. Each file type
* detector's {@link FileTypeDetector#probeContentType probeContentType} is
* invoked, in turn, to probe the file type. If the file is recognized then
* the content type is returned. If the file is not recognized by any of the
* installed file type detectors then a system-default file type detector is
* invoked to guess the content type.
*
*
A given invocation of the Java virtual machine maintains a system-wide
* list of file type detectors. Installed file type detectors are loaded
* using the service-provider loading facility defined by the {@link ServiceLoader}
* class. Installed file type detectors are loaded using the system class
* loader. If the system class loader cannot be found then the extension class
* loader is used; If the extension class loader cannot be found then the
* bootstrap class loader is used. File type detectors are typically installed
* by placing them in a JAR file on the application class path or in the
* extension directory, the JAR file contains a provider-configuration file
* named {@code java.nio.file.spi.FileTypeDetector} in the resource directory
* {@code META-INF/services}, and the file lists one or more fully-qualified
* names of concrete subclass of {@code FileTypeDetector } that have a zero
* argument constructor. If the process of locating or instantiating the
* installed file type detectors fails then an unspecified error is thrown.
* The ordering that installed providers are located is implementation
* specific.
*
*
The return value of this method is the string form of the value of a
* Multipurpose Internet Mail Extension (MIME) content type as
* defined by RFC 2045:
* Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet
* Message Bodies. The string is guaranteed to be parsable according
* to the grammar in the RFC.
*
* @param path
* the path to the file to probe
*
* @return The content type of the file, or {@code null} if the content
* type cannot be determined
*
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* If a security manager is installed and it denies an unspecified
* permission required by a file type detector implementation.
*/
public static String probeContentType(Path path)
throws IOException
{
// try installed file type detectors
for (FileTypeDetector detector: FileTypeDetectors.installeDetectors) {
String result = detector.probeContentType(path);
if (result != null)
return result;
}
// fallback to default
return FileTypeDetectors.defaultFileTypeDetector.probeContentType(path);
}
// -- File Attributes --
/**
* Returns a file attribute view of a given type.
*
*
A file attribute view provides a read-only or updatable view of a
* set of file attributes. This method is intended to be used where the file
* attribute view defines type-safe methods to read or update the file
* attributes. The {@code type} parameter is the type of the attribute view
* required and the method returns an instance of that type if supported.
* The {@link BasicFileAttributeView} type supports access to the basic
* attributes of a file. Invoking this method to select a file attribute
* view of that type will always return an instance of that class.
*
*
The {@code options} array may be used to indicate how symbolic links
* are handled by the resulting file attribute view for the case that the
* file is a symbolic link. By default, symbolic links are followed. If the
* option {@link LinkOption#NOFOLLOW_LINKS NOFOLLOW_LINKS} is present then
* symbolic links are not followed. This option is ignored by implementations
* that do not support symbolic links.
*
*
Usage Example:
* Suppose we want read or set a file's ACL, if supported:
*
* Path path = ...
* AclFileAttributeView view = Files.getFileAttributeView(path, AclFileAttributeView.class);
* if (view != null) {
* List<AclEntry> acl = view.getAcl();
* :
* }
*
*
* @param
* The {@code FileAttributeView} type
* @param path
* the path to the file
* @param type
* the {@code Class} object corresponding to the file attribute view
* @param options
* options indicating how symbolic links are handled
*
* @return a file attribute view of the specified type, or {@code null} if
* the attribute view type is not available
*/
public static V getFileAttributeView(Path path,
Class type,
LinkOption... options)
{
return provider(path).getFileAttributeView(path, type, options);
}
/**
* Reads a file's attributes as a bulk operation.
*
* The {@code type} parameter is the type of the attributes required
* and this method returns an instance of that type if supported. All
* implementations support a basic set of file attributes and so invoking
* this method with a {@code type} parameter of {@code
* BasicFileAttributes.class} will not throw {@code
* UnsupportedOperationException}.
*
*
The {@code options} array may be used to indicate how symbolic links
* are handled for the case that the file is a symbolic link. By default,
* symbolic links are followed and the file attribute of the final target
* of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
* NOFOLLOW_LINKS} is present then symbolic links are not followed.
*
*
It is implementation specific if all file attributes are read as an
* atomic operation with respect to other file system operations.
*
*
Usage Example:
* Suppose we want to read a file's attributes in bulk:
*
* Path path = ...
* BasicFileAttributes attrs = Files.readAttributes(path, BasicFileAttributes.class);
*
* Alternatively, suppose we want to read file's POSIX attributes without
* following symbolic links:
*
* PosixFileAttributes attrs = Files.readAttributes(path, PosixFileAttributes.class, NOFOLLOW_LINKS);
*
*
* @param
* The {@code BasicFileAttributes} type
* @param path
* the path to the file
* @param type
* the {@code Class} of the file attributes required
* to read
* @param options
* options indicating how symbolic links are handled
*
* @return the file attributes
*
* @throws UnsupportedOperationException
* if an attributes of the given type are not supported
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, a security manager is
* installed, its {@link SecurityManager#checkRead(String) checkRead}
* method is invoked to check read access to the file. If this
* method is invoked to read security sensitive attributes then the
* security manager may be invoke to check for additional permissions.
*/
public static A readAttributes(Path path,
Class type,
LinkOption... options)
throws IOException
{
return provider(path).readAttributes(path, type, options);
}
/**
* Sets the value of a file attribute.
*
* The {@code attribute} parameter identifies the attribute to be set
* and takes the form:
*
* [view-name:]attribute-name
*
* where square brackets [...] delineate an optional component and the
* character {@code ':'} stands for itself.
*
* view-name is the {@link FileAttributeView#name name} of a {@link
* FileAttributeView} that identifies a set of file attributes. If not
* specified then it defaults to {@code "basic"}, the name of the file
* attribute view that identifies the basic set of file attributes common to
* many file systems. attribute-name is the name of the attribute
* within the set.
*
*
The {@code options} array may be used to indicate how symbolic links
* are handled for the case that the file is a symbolic link. By default,
* symbolic links are followed and the file attribute of the final target
* of the link is set. If the option {@link LinkOption#NOFOLLOW_LINKS
* NOFOLLOW_LINKS} is present then symbolic links are not followed.
*
*
Usage Example:
* Suppose we want to set the DOS "hidden" attribute:
*
* Path path = ...
* Files.setAttribute(path, "dos:hidden", true);
*
*
* @param path
* the path to the file
* @param attribute
* the attribute to set
* @param value
* the attribute value
* @param options
* options indicating how symbolic links are handled
*
* @return the {@code path} parameter
*
* @throws UnsupportedOperationException
* if the attribute view is not available
* @throws IllegalArgumentException
* if the attribute name is not specified, or is not recognized, or
* the attribute value is of the correct type but has an
* inappropriate value
* @throws ClassCastException
* if the attribute value is not of the expected type or is a
* collection containing elements that are not of the expected
* type
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, its {@link SecurityManager#checkWrite(String) checkWrite}
* method denies write access to the file. If this method is invoked
* to set security sensitive attributes then the security manager
* may be invoked to check for additional permissions.
*/
public static Path setAttribute(Path path, String attribute, Object value,
LinkOption... options)
throws IOException
{
provider(path).setAttribute(path, attribute, value, options);
return path;
}
/**
* Reads the value of a file attribute.
*
* The {@code attribute} parameter identifies the attribute to be read
* and takes the form:
*
* [view-name:]attribute-name
*
* where square brackets [...] delineate an optional component and the
* character {@code ':'} stands for itself.
*
* view-name is the {@link FileAttributeView#name name} of a {@link
* FileAttributeView} that identifies a set of file attributes. If not
* specified then it defaults to {@code "basic"}, the name of the file
* attribute view that identifies the basic set of file attributes common to
* many file systems. attribute-name is the name of the attribute.
*
*
The {@code options} array may be used to indicate how symbolic links
* are handled for the case that the file is a symbolic link. By default,
* symbolic links are followed and the file attribute of the final target
* of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
* NOFOLLOW_LINKS} is present then symbolic links are not followed.
*
*
Usage Example:
* Suppose we require the user ID of the file owner on a system that
* supports a "{@code unix}" view:
*
* Path path = ...
* int uid = (Integer)Files.getAttribute(path, "unix:uid");
*
*
* @param path
* the path to the file
* @param attribute
* the attribute to read
* @param options
* options indicating how symbolic links are handled
*
* @return the attribute value
*
* @throws UnsupportedOperationException
* if the attribute view is not available
* @throws IllegalArgumentException
* if the attribute name is not specified or is not recognized
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, its {@link SecurityManager#checkRead(String) checkRead}
* method denies read access to the file. If this method is invoked
* to read security sensitive attributes then the security manager
* may be invoked to check for additional permissions.
*/
public static Object getAttribute(Path path, String attribute,
LinkOption... options)
throws IOException
{
// only one attribute should be read
if (attribute.indexOf('*') >= 0 || attribute.indexOf(',') >= 0)
throw new IllegalArgumentException(attribute);
Map map = readAttributes(path, attribute, options);
assert map.size() == 1;
String name;
int pos = attribute.indexOf(':');
if (pos == -1) {
name = attribute;
} else {
name = (pos == attribute.length()) ? "" : attribute.substring(pos+1);
}
return map.get(name);
}
/**
* Reads a set of file attributes as a bulk operation.
*
* The {@code attributes} parameter identifies the attributes to be read
* and takes the form:
*
* [view-name:]attribute-list
*
* where square brackets [...] delineate an optional component and the
* character {@code ':'} stands for itself.
*
* view-name is the {@link FileAttributeView#name name} of a {@link
* FileAttributeView} that identifies a set of file attributes. If not
* specified then it defaults to {@code "basic"}, the name of the file
* attribute view that identifies the basic set of file attributes common to
* many file systems.
*
*
The attribute-list component is a comma separated list of
* zero or more names of attributes to read. If the list contains the value
* {@code "*"} then all attributes are read. Attributes that are not supported
* are ignored and will not be present in the returned map. It is
* implementation specific if all attributes are read as an atomic operation
* with respect to other file system operations.
*
*
The following examples demonstrate possible values for the {@code
* attributes} parameter:
*
*
*
*
* {@code "*"}
* Read all {@link BasicFileAttributes basic-file-attributes}.
*
*
* {@code "size,lastModifiedTime,lastAccessTime"}
* Reads the file size, last modified time, and last access time
* attributes.
*
*
* {@code "posix:*"}
* Read all {@link PosixFileAttributes POSIX-file-attributes}.
*
*
* {@code "posix:permissions,owner,size"}
* Reads the POSX file permissions, owner, and file size.
*
*
*
*
* The {@code options} array may be used to indicate how symbolic links
* are handled for the case that the file is a symbolic link. By default,
* symbolic links are followed and the file attribute of the final target
* of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
* NOFOLLOW_LINKS} is present then symbolic links are not followed.
*
* @param path
* the path to the file
* @param attributes
* the attributes to read
* @param options
* options indicating how symbolic links are handled
*
* @return a map of the attributes returned; The map's keys are the
* attribute names, its values are the attribute values
*
* @throws UnsupportedOperationException
* if the attribute view is not available
* @throws IllegalArgumentException
* if no attributes are specified or an unrecognized attributes is
* specified
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, its {@link SecurityManager#checkRead(String) checkRead}
* method denies read access to the file. If this method is invoked
* to read security sensitive attributes then the security manager
* may be invoke to check for additional permissions.
*/
public static Map readAttributes(Path path, String attributes,
LinkOption... options)
throws IOException
{
return provider(path).readAttributes(path, attributes, options);
}
/**
* Returns a file's POSIX file permissions.
*
* The {@code path} parameter is associated with a {@code FileSystem}
* that supports the {@link PosixFileAttributeView}. This attribute view
* provides access to file attributes commonly associated with files on file
* systems used by operating systems that implement the Portable Operating
* System Interface (POSIX) family of standards.
*
*
The {@code options} array may be used to indicate how symbolic links
* are handled for the case that the file is a symbolic link. By default,
* symbolic links are followed and the file attribute of the final target
* of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
* NOFOLLOW_LINKS} is present then symbolic links are not followed.
*
* @param path
* the path to the file
* @param options
* options indicating how symbolic links are handled
*
* @return the file permissions
*
* @throws UnsupportedOperationException
* if the associated file system does not support the {@code
* PosixFileAttributeView}
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, a security manager is
* installed, and it denies {@link RuntimePermission}("accessUserInformation")
* or its {@link SecurityManager#checkRead(String) checkRead} method
* denies read access to the file.
*/
public static Set getPosixFilePermissions(Path path,
LinkOption... options)
throws IOException
{
return readAttributes(path, PosixFileAttributes.class, options).permissions();
}
/**
* Sets a file's POSIX permissions.
*
* The {@code path} parameter is associated with a {@code FileSystem}
* that supports the {@link PosixFileAttributeView}. This attribute view
* provides access to file attributes commonly associated with files on file
* systems used by operating systems that implement the Portable Operating
* System Interface (POSIX) family of standards.
*
* @param path
* The path to the file
* @param perms
* The new set of permissions
*
* @return The path
*
* @throws UnsupportedOperationException
* if the associated file system does not support the {@code
* PosixFileAttributeView}
* @throws ClassCastException
* if the sets contains elements that are not of type {@code
* PosixFilePermission}
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, it denies {@link RuntimePermission}("accessUserInformation")
* or its {@link SecurityManager#checkWrite(String) checkWrite}
* method denies write access to the file.
*/
public static Path setPosixFilePermissions(Path path,
Set perms)
throws IOException
{
PosixFileAttributeView view =
getFileAttributeView(path, PosixFileAttributeView.class);
if (view == null)
throw new UnsupportedOperationException();
view.setPermissions(perms);
return path;
}
/**
* Returns the owner of a file.
*
* The {@code path} parameter is associated with a file system that
* supports {@link FileOwnerAttributeView}. This file attribute view provides
* access to a file attribute that is the owner of the file.
*
* @param path
* The path to the file
* @param options
* options indicating how symbolic links are handled
*
* @return A user principal representing the owner of the file
*
* @throws UnsupportedOperationException
* if the associated file system does not support the {@code
* FileOwnerAttributeView}
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, it denies {@link RuntimePermission}("accessUserInformation")
* or its {@link SecurityManager#checkRead(String) checkRead} method
* denies read access to the file.
*/
public static UserPrincipal getOwner(Path path, LinkOption... options) throws IOException {
FileOwnerAttributeView view =
getFileAttributeView(path, FileOwnerAttributeView.class, options);
if (view == null)
throw new UnsupportedOperationException();
return view.getOwner();
}
/**
* Updates the file owner.
*
*
The {@code path} parameter is associated with a file system that
* supports {@link FileOwnerAttributeView}. This file attribute view provides
* access to a file attribute that is the owner of the file.
*
*
Usage Example:
* Suppose we want to make "joe" the owner of a file:
*
* Path path = ...
* UserPrincipalLookupService lookupService =
* provider(path).getUserPrincipalLookupService();
* UserPrincipal joe = lookupService.lookupPrincipalByName("joe");
* Files.setOwner(path, joe);
*
*
* @param path
* The path to the file
* @param owner
* The new file owner
*
* @return The path
*
* @throws UnsupportedOperationException
* if the associated file system does not support the {@code
* FileOwnerAttributeView}
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, it denies {@link RuntimePermission}("accessUserInformation")
* or its {@link SecurityManager#checkWrite(String) checkWrite}
* method denies write access to the file.
*
* @see FileSystem#getUserPrincipalLookupService
* @see java.nio.file.attribute.UserPrincipalLookupService
*/
public static Path setOwner(Path path, UserPrincipal owner)
throws IOException
{
FileOwnerAttributeView view =
getFileAttributeView(path, FileOwnerAttributeView.class);
if (view == null)
throw new UnsupportedOperationException();
view.setOwner(owner);
return path;
}
/**
* Tests whether a file is a symbolic link.
*
* Where it is required to distinguish an I/O exception from the case
* that the file is not a symbolic link then the file attributes can be
* read with the {@link #readAttributes(Path,Class,LinkOption[])
* readAttributes} method and the file type tested with the {@link
* BasicFileAttributes#isSymbolicLink} method.
*
* @param path The path to the file
*
* @return {@code true} if the file is a symbolic link; {@code false} if
* the file does not exist, is not a symbolic link, or it cannot
* be determined if the file is a symbolic link or not.
*
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, its {@link SecurityManager#checkRead(String) checkRead}
* method denies read access to the file.
*/
public static boolean isSymbolicLink(Path path) {
try {
return readAttributes(path,
BasicFileAttributes.class,
LinkOption.NOFOLLOW_LINKS).isSymbolicLink();
} catch (IOException ioe) {
return false;
}
}
/**
* Tests whether a file is a directory.
*
*
The {@code options} array may be used to indicate how symbolic links
* are handled for the case that the file is a symbolic link. By default,
* symbolic links are followed and the file attribute of the final target
* of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
* NOFOLLOW_LINKS} is present then symbolic links are not followed.
*
*
Where it is required to distinguish an I/O exception from the case
* that the file is not a directory then the file attributes can be
* read with the {@link #readAttributes(Path,Class,LinkOption[])
* readAttributes} method and the file type tested with the {@link
* BasicFileAttributes#isDirectory} method.
*
* @param path
* the path to the file to test
* @param options
* options indicating how symbolic links are handled
*
* @return {@code true} if the file is a directory; {@code false} if
* the file does not exist, is not a directory, or it cannot
* be determined if the file is a directory or not.
*
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, its {@link SecurityManager#checkRead(String) checkRead}
* method denies read access to the file.
*/
public static boolean isDirectory(Path path, LinkOption... options) {
try {
return readAttributes(path, BasicFileAttributes.class, options).isDirectory();
} catch (IOException ioe) {
return false;
}
}
/**
* Tests whether a file is a regular file with opaque content.
*
*
The {@code options} array may be used to indicate how symbolic links
* are handled for the case that the file is a symbolic link. By default,
* symbolic links are followed and the file attribute of the final target
* of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
* NOFOLLOW_LINKS} is present then symbolic links are not followed.
*
*
Where it is required to distinguish an I/O exception from the case
* that the file is not a regular file then the file attributes can be
* read with the {@link #readAttributes(Path,Class,LinkOption[])
* readAttributes} method and the file type tested with the {@link
* BasicFileAttributes#isRegularFile} method.
*
* @param path
* the path to the file
* @param options
* options indicating how symbolic links are handled
*
* @return {@code true} if the file is a regular file; {@code false} if
* the file does not exist, is not a regular file, or it
* cannot be determined if the file is a regular file or not.
*
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, its {@link SecurityManager#checkRead(String) checkRead}
* method denies read access to the file.
*/
public static boolean isRegularFile(Path path, LinkOption... options) {
try {
return readAttributes(path, BasicFileAttributes.class, options).isRegularFile();
} catch (IOException ioe) {
return false;
}
}
/**
* Returns a file's last modified time.
*
*
The {@code options} array may be used to indicate how symbolic links
* are handled for the case that the file is a symbolic link. By default,
* symbolic links are followed and the file attribute of the final target
* of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
* NOFOLLOW_LINKS} is present then symbolic links are not followed.
*
* @param path
* the path to the file
* @param options
* options indicating how symbolic links are handled
*
* @return a {@code FileTime} representing the time the file was last
* modified, or an implementation specific default when a time
* stamp to indicate the time of last modification is not supported
* by the file system
*
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, its {@link SecurityManager#checkRead(String) checkRead}
* method denies read access to the file.
*
* @see BasicFileAttributes#lastModifiedTime
*/
public static FileTime getLastModifiedTime(Path path, LinkOption... options)
throws IOException
{
return readAttributes(path, BasicFileAttributes.class, options).lastModifiedTime();
}
/**
* Updates a file's last modified time attribute. The file time is converted
* to the epoch and precision supported by the file system. Converting from
* finer to coarser granularities result in precision loss. The behavior of
* this method when attempting to set the last modified time when it is not
* supported by the file system or is outside the range supported by the
* underlying file store is not defined. It may or not fail by throwing an
* {@code IOException}.
*
*
Usage Example:
* Suppose we want to set the last modified time to the current time:
*
* Path path = ...
* FileTime now = FileTime.fromMillis(System.currentTimeMillis());
* Files.setLastModifiedTime(path, now);
*
*
* @param path
* the path to the file
* @param time
* the new last modified time
*
* @return the path
*
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, the security manager's {@link
* SecurityManager#checkWrite(String) checkWrite} method is invoked
* to check write access to file
*
* @see BasicFileAttributeView#setTimes
*/
public static Path setLastModifiedTime(Path path, FileTime time)
throws IOException
{
getFileAttributeView(path, BasicFileAttributeView.class)
.setTimes(time, null, null);
return path;
}
/**
* Returns the size of a file (in bytes). The size may differ from the
* actual size on the file system due to compression, support for sparse
* files, or other reasons. The size of files that are not {@link
* #isRegularFile regular} files is implementation specific and
* therefore unspecified.
*
* @param path
* the path to the file
*
* @return the file size, in bytes
*
* @throws IOException
* if an I/O error occurs
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, its {@link SecurityManager#checkRead(String) checkRead}
* method denies read access to the file.
*
* @see BasicFileAttributes#size
*/
public static long size(Path path) throws IOException {
return readAttributes(path, BasicFileAttributes.class).size();
}
// -- Accessibility --
/**
* Returns {@code false} if NOFOLLOW_LINKS is present.
*/
private static boolean followLinks(LinkOption... options) {
boolean followLinks = true;
for (LinkOption opt: options) {
if (opt == LinkOption.NOFOLLOW_LINKS) {
followLinks = false;
continue;
}
if (opt == null)
throw new NullPointerException();
throw new AssertionError("Should not get here");
}
return followLinks;
}
/**
* Tests whether a file exists.
*
* The {@code options} parameter may be used to indicate how symbolic links
* are handled for the case that the file is a symbolic link. By default,
* symbolic links are followed. If the option {@link LinkOption#NOFOLLOW_LINKS
* NOFOLLOW_LINKS} is present then symbolic links are not followed.
*
*
Note that the result of this method is immediately outdated. If this
* method indicates the file exists then there is no guarantee that a
* subsequence access will succeed. Care should be taken when using this
* method in security sensitive applications.
*
* @param path
* the path to the file to test
* @param options
* options indicating how symbolic links are handled
* .
* @return {@code true} if the file exists; {@code false} if the file does
* not exist or its existence cannot be determined.
*
* @throws SecurityException
* In the case of the default provider, the {@link
* SecurityManager#checkRead(String)} is invoked to check
* read access to the file.
*
* @see #notExists
*/
public static boolean exists(Path path, LinkOption... options) {
try {
if (followLinks(options)) {
provider(path).checkAccess(path);
} else {
// attempt to read attributes without following links
readAttributes(path, BasicFileAttributes.class,
LinkOption.NOFOLLOW_LINKS);
}
// file exists
return true;
} catch (IOException x) {
// does not exist or unable to determine if file exists
return false;
}
}
/**
* Tests whether the file located by this path does not exist. This method
* is intended for cases where it is required to take action when it can be
* confirmed that a file does not exist.
*
*
The {@code options} parameter may be used to indicate how symbolic links
* are handled for the case that the file is a symbolic link. By default,
* symbolic links are followed. If the option {@link LinkOption#NOFOLLOW_LINKS
* NOFOLLOW_LINKS} is present then symbolic links are not followed.
*
*
Note that this method is not the complement of the {@link #exists
* exists} method. Where it is not possible to determine if a file exists
* or not then both methods return {@code false}. As with the {@code exists}
* method, the result of this method is immediately outdated. If this
* method indicates the file does exist then there is no guarantee that a
* subsequence attempt to create the file will succeed. Care should be taken
* when using this method in security sensitive applications.
*
* @param path
* the path to the file to test
* @param options
* options indicating how symbolic links are handled
*
* @return {@code true} if the file does not exist; {@code false} if the
* file exists or its existence cannot be determined
*
* @throws SecurityException
* In the case of the default provider, the {@link
* SecurityManager#checkRead(String)} is invoked to check
* read access to the file.
*/
public static boolean notExists(Path path, LinkOption... options) {
try {
if (followLinks(options)) {
provider(path).checkAccess(path);
} else {
// attempt to read attributes without following links
readAttributes(path, BasicFileAttributes.class,
LinkOption.NOFOLLOW_LINKS);
}
// file exists
return false;
} catch (NoSuchFileException x) {
// file confirmed not to exist
return true;
} catch (IOException x) {
return false;
}
}
/**
* Used by isReadbale, isWritable, isExecutable to test access to a file.
*/
private static boolean isAccessible(Path path, AccessMode... modes) {
try {
provider(path).checkAccess(path, modes);
return true;
} catch (IOException x) {
return false;
}
}
/**
* Tests whether a file is readable. This method checks that a file exists
* and that this Java virtual machine has appropriate privileges that would
* allow it open the file for reading. Depending on the implementation, this
* method may require to read file permissions, access control lists, or
* other file attributes in order to check the effective access to the file.
* Consequently, this method may not be atomic with respect to other file
* system operations.
*
*
Note that the result of this method is immediately outdated, there is
* no guarantee that a subsequent attempt to open the file for reading will
* succeed (or even that it will access the same file). Care should be taken
* when using this method in security sensitive applications.
*
* @param path
* the path to the file to check
*
* @return {@code true} if the file exists and is readable; {@code false}
* if the file does not exist, read access would be denied because
* the Java virtual machine has insufficient privileges, or access
* cannot be determined
*
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkRead(String) checkRead}
* is invoked to check read access to the file.
*/
public static boolean isReadable(Path path) {
return isAccessible(path, AccessMode.READ);
}
/**
* Tests whether a file is writable. This method checks that a file exists
* and that this Java virtual machine has appropriate privileges that would
* allow it open the file for writing. Depending on the implementation, this
* method may require to read file permissions, access control lists, or
* other file attributes in order to check the effective access to the file.
* Consequently, this method may not be atomic with respect to other file
* system operations.
*
*
Note that result of this method is immediately outdated, there is no
* guarantee that a subsequent attempt to open the file for writing will
* succeed (or even that it will access the same file). Care should be taken
* when using this method in security sensitive applications.
*
* @param path
* the path to the file to check
*
* @return {@code true} if the file exists and is writable; {@code false}
* if the file does not exist, write access would be denied because
* the Java virtual machine has insufficient privileges, or access
* cannot be determined
*
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkWrite(String) checkWrite}
* is invoked to check write access to the file.
*/
public static boolean isWritable(Path path) {
return isAccessible(path, AccessMode.WRITE);
}
/**
* Tests whether a file is executable. This method checks that a file exists
* and that this Java virtual machine has appropriate privileges to {@link
* Runtime#exec execute} the file. The semantics may differ when checking
* access to a directory. For example, on UNIX systems, checking for
* execute access checks that the Java virtual machine has permission to
* search the directory in order to access file or subdirectories.
*
*
Depending on the implementation, this method may require to read file
* permissions, access control lists, or other file attributes in order to
* check the effective access to the file. Consequently, this method may not
* be atomic with respect to other file system operations.
*
*
Note that the result of this method is immediately outdated, there is
* no guarantee that a subsequent attempt to execute the file will succeed
* (or even that it will access the same file). Care should be taken when
* using this method in security sensitive applications.
*
* @param path
* the path to the file to check
*
* @return {@code true} if the file exists and is executable; {@code false}
* if the file does not exist, execute access would be denied because
* the Java virtual machine has insufficient privileges, or access
* cannot be determined
*
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkExec(String)
* checkExec} is invoked to check execute access to the file.
*/
public static boolean isExecutable(Path path) {
return isAccessible(path, AccessMode.EXECUTE);
}
// -- Recursive operations --
/**
* Walks a file tree.
*
*
This method walks a file tree rooted at a given starting file. The
* file tree traversal is depth-first with the given {@link
* FileVisitor} invoked for each file encountered. File tree traversal
* completes when all accessible files in the tree have been visited, or a
* visit method returns a result of {@link FileVisitResult#TERMINATE
* TERMINATE}. Where a visit method terminates due an {@code IOException},
* an uncaught error, or runtime exception, then the traversal is terminated
* and the error or exception is propagated to the caller of this method.
*
*
For each file encountered this method attempts to read its {@link
* java.nio.file.attribute.BasicFileAttributes}. If the file is not a
* directory then the {@link FileVisitor#visitFile visitFile} method is
* invoked with the file attributes. If the file attributes cannot be read,
* due to an I/O exception, then the {@link FileVisitor#visitFileFailed
* visitFileFailed} method is invoked with the I/O exception.
*
*
Where the file is a directory, and the directory could not be opened,
* then the {@code visitFileFailed} method is invoked with the I/O exception,
* after which, the file tree walk continues, by default, at the next
* sibling of the directory.
*
*
Where the directory is opened successfully, then the entries in the
* directory, and their descendants are visited. When all entries
* have been visited, or an I/O error occurs during iteration of the
* directory, then the directory is closed and the visitor's {@link
* FileVisitor#postVisitDirectory postVisitDirectory} method is invoked.
* The file tree walk then continues, by default, at the next sibling
* of the directory.
*
*
By default, symbolic links are not automatically followed by this
* method. If the {@code options} parameter contains the {@link
* FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then symbolic links are
* followed. When following links, and the attributes of the target cannot
* be read, then this method attempts to get the {@code BasicFileAttributes}
* of the link. If they can be read then the {@code visitFile} method is
* invoked with the attributes of the link (otherwise the {@code visitFileFailed}
* method is invoked as specified above).
*
*
If the {@code options} parameter contains the {@link
* FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then this method keeps
* track of directories visited so that cycles can be detected. A cycle
* arises when there is an entry in a directory that is an ancestor of the
* directory. Cycle detection is done by recording the {@link
* java.nio.file.attribute.BasicFileAttributes#fileKey file-key} of directories,
* or if file keys are not available, by invoking the {@link #isSameFile
* isSameFile} method to test if a directory is the same file as an
* ancestor. When a cycle is detected it is treated as an I/O error, and the
* {@link FileVisitor#visitFileFailed visitFileFailed} method is invoked with
* an instance of {@link FileSystemLoopException}.
*
*
The {@code maxDepth} parameter is the maximum number of levels of
* directories to visit. A value of {@code 0} means that only the starting
* file is visited, unless denied by the security manager. A value of
* {@link Integer#MAX_VALUE MAX_VALUE} may be used to indicate that all
* levels should be visited. The {@code visitFile} method is invoked for all
* files, including directories, encountered at {@code maxDepth}, unless the
* basic file attributes cannot be read, in which case the {@code
* visitFileFailed} method is invoked.
*
*
If a visitor returns a result of {@code null} then {@code
* NullPointerException} is thrown.
*
*
When a security manager is installed and it denies access to a file
* (or directory), then it is ignored and the visitor is not invoked for
* that file (or directory).
*
* @param start
* the starting file
* @param options
* options to configure the traversal
* @param maxDepth
* the maximum number of directory levels to visit
* @param visitor
* the file visitor to invoke for each file
*
* @return the starting file
*
* @throws IllegalArgumentException
* if the {@code maxDepth} parameter is negative
* @throws SecurityException
* If the security manager denies access to the starting file.
* In the case of the default provider, the {@link
* SecurityManager#checkRead(String) checkRead} method is invoked
* to check read access to the directory.
* @throws IOException
* if an I/O error is thrown by a visitor method
*/
public static Path walkFileTree(Path start,
Set options,
int maxDepth,
FileVisitor visitor)
throws IOException
{
/**
* Create a FileTreeWalker to walk the file tree, invoking the visitor
* for each event.
*/
try (FileTreeWalker walker = new FileTreeWalker(options, maxDepth)) {
FileTreeWalker.Event ev = walker.walk(start);
do {
FileVisitResult result;
switch (ev.type()) {
case ENTRY :
IOException ioe = ev.ioeException();
if (ioe == null) {
assert ev.attributes() != null;
result = visitor.visitFile(ev.file(), ev.attributes());
} else {
result = visitor.visitFileFailed(ev.file(), ioe);
}
break;
case START_DIRECTORY :
result = visitor.preVisitDirectory(ev.file(), ev.attributes());
// if SKIP_SIBLINGS and SKIP_SUBTREE is returned then
// there shouldn't be any more events for the current
// directory.
if (result == FileVisitResult.SKIP_SUBTREE ||
result == FileVisitResult.SKIP_SIBLINGS)
walker.pop();
break;
case END_DIRECTORY :
result = visitor.postVisitDirectory(ev.file(), ev.ioeException());
// SKIP_SIBLINGS is a no-op for postVisitDirectory
if (result == FileVisitResult.SKIP_SIBLINGS)
result = FileVisitResult.CONTINUE;
break;
default :
throw new AssertionError("Should not get here");
}
if (Objects.requireNonNull(result) != FileVisitResult.CONTINUE) {
if (result == FileVisitResult.TERMINATE) {
break;
} else if (result == FileVisitResult.SKIP_SIBLINGS) {
walker.skipRemainingSiblings();
}
}
ev = walker.next();
} while (ev != null);
}
return start;
}
/**
* Walks a file tree.
*
* This method works as if invoking it were equivalent to evaluating the
* expression:
*
* walkFileTree(start, EnumSet.noneOf(FileVisitOption.class), Integer.MAX_VALUE, visitor)
*
* In other words, it does not follow symbolic links, and visits all levels
* of the file tree.
*
* @param start
* the starting file
* @param visitor
* the file visitor to invoke for each file
*
* @return the starting file
*
* @throws SecurityException
* If the security manager denies access to the starting file.
* In the case of the default provider, the {@link
* SecurityManager#checkRead(String) checkRead} method is invoked
* to check read access to the directory.
* @throws IOException
* if an I/O error is thrown by a visitor method
*/
public static Path walkFileTree(Path start, FileVisitor visitor)
throws IOException
{
return walkFileTree(start,
EnumSet.noneOf(FileVisitOption.class),
Integer.MAX_VALUE,
visitor);
}
// -- Utility methods for simple usages --
// buffer size used for reading and writing
private static final int BUFFER_SIZE = 8192;
/**
* Opens a file for reading, returning a {@code BufferedReader} that may be
* used to read text from the file in an efficient manner. Bytes from the
* file are decoded into characters using the specified charset. Reading
* commences at the beginning of the file.
*
* The {@code Reader} methods that read from the file throw {@code
* IOException} if a malformed or unmappable byte sequence is read.
*
* @param path
* the path to the file
* @param cs
* the charset to use for decoding
*
* @return a new buffered reader, with default buffer size, to read text
* from the file
*
* @throws IOException
* if an I/O error occurs opening the file
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkRead(String) checkRead}
* method is invoked to check read access to the file.
*
* @see #readAllLines
*/
public static BufferedReader newBufferedReader(Path path, Charset cs)
throws IOException
{
CharsetDecoder decoder = cs.newDecoder();
Reader reader = new InputStreamReader(newInputStream(path), decoder);
return new BufferedReader(reader);
}
/**
* Opens a file for reading, returning a {@code BufferedReader} to read text
* from the file in an efficient manner. Bytes from the file are decoded into
* characters using the {@link StandardCharsets#UTF_8 UTF-8} {@link Charset
* charset}.
*
*
This method works as if invoking it were equivalent to evaluating the
* expression:
*
{@code
* Files.newBufferedReader(path, StandardCharsets.UTF_8)
* }
*
* @param path
* the path to the file
*
* @return a new buffered reader, with default buffer size, to read text
* from the file
*
* @throws IOException
* if an I/O error occurs opening the file
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkRead(String) checkRead}
* method is invoked to check read access to the file.
*
* @since 1.8
*/
public static BufferedReader newBufferedReader(Path path) throws IOException {
return newBufferedReader(path, StandardCharsets.UTF_8);
}
/**
* Opens or creates a file for writing, returning a {@code BufferedWriter}
* that may be used to write text to the file in an efficient manner.
* The {@code options} parameter specifies how the the file is created or
* opened. If no options are present then this method works as if the {@link
* StandardOpenOption#CREATE CREATE}, {@link
* StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link
* StandardOpenOption#WRITE WRITE} options are present. In other words, it
* opens the file for writing, creating the file if it doesn't exist, or
* initially truncating an existing {@link #isRegularFile regular-file} to
* a size of {@code 0} if it exists.
*
* The {@code Writer} methods to write text throw {@code IOException}
* if the text cannot be encoded using the specified charset.
*
* @param path
* the path to the file
* @param cs
* the charset to use for encoding
* @param options
* options specifying how the file is opened
*
* @return a new buffered writer, with default buffer size, to write text
* to the file
*
* @throws IOException
* if an I/O error occurs opening or creating the file
* @throws UnsupportedOperationException
* if an unsupported option is specified
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkWrite(String) checkWrite}
* method is invoked to check write access to the file.
*
* @see #write(Path,Iterable,Charset,OpenOption[])
*/
public static BufferedWriter newBufferedWriter(Path path, Charset cs,
OpenOption... options)
throws IOException
{
CharsetEncoder encoder = cs.newEncoder();
Writer writer = new OutputStreamWriter(newOutputStream(path, options), encoder);
return new BufferedWriter(writer);
}
/**
* Opens or creates a file for writing, returning a {@code BufferedWriter}
* to write text to the file in an efficient manner. The text is encoded
* into bytes for writing using the {@link StandardCharsets#UTF_8 UTF-8}
* {@link Charset charset}.
*
*
This method works as if invoking it were equivalent to evaluating the
* expression:
*
{@code
* Files.newBufferedWriter(path, StandardCharsets.UTF_8, options)
* }
*
* @param path
* the path to the file
* @param options
* options specifying how the file is opened
*
* @return a new buffered writer, with default buffer size, to write text
* to the file
*
* @throws IOException
* if an I/O error occurs opening or creating the file
* @throws UnsupportedOperationException
* if an unsupported option is specified
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkWrite(String) checkWrite}
* method is invoked to check write access to the file.
*
* @since 1.8
*/
public static BufferedWriter newBufferedWriter(Path path, OpenOption... options) throws IOException {
return newBufferedWriter(path, StandardCharsets.UTF_8, options);
}
/**
* Reads all bytes from an input stream and writes them to an output stream.
*/
private static long copy(InputStream source, OutputStream sink)
throws IOException
{
long nread = 0L;
byte[] buf = new byte[BUFFER_SIZE];
int n;
while ((n = source.read(buf)) > 0) {
sink.write(buf, 0, n);
nread += n;
}
return nread;
}
/**
* Copies all bytes from an input stream to a file. On return, the input
* stream will be at end of stream.
*
* By default, the copy fails if the target file already exists or is a
* symbolic link. If the {@link StandardCopyOption#REPLACE_EXISTING
* REPLACE_EXISTING} option is specified, and the target file already exists,
* then it is replaced if it is not a non-empty directory. If the target
* file exists and is a symbolic link, then the symbolic link is replaced.
* In this release, the {@code REPLACE_EXISTING} option is the only option
* required to be supported by this method. Additional options may be
* supported in future releases.
*
*
If an I/O error occurs reading from the input stream or writing to
* the file, then it may do so after the target file has been created and
* after some bytes have been read or written. Consequently the input
* stream may not be at end of stream and may be in an inconsistent state.
* It is strongly recommended that the input stream be promptly closed if an
* I/O error occurs.
*
*
This method may block indefinitely reading from the input stream (or
* writing to the file). The behavior for the case that the input stream is
* asynchronously closed or the thread interrupted during the copy is
* highly input stream and file system provider specific and therefore not
* specified.
*
*
Usage example: Suppose we want to capture a web page and save
* it to a file:
*
* Path path = ...
* URI u = URI.create("http://java.sun.com/");
* try (InputStream in = u.toURL().openStream()) {
* Files.copy(in, path);
* }
*
*
* @param in
* the input stream to read from
* @param target
* the path to the file
* @param options
* options specifying how the copy should be done
*
* @return the number of bytes read or written
*
* @throws IOException
* if an I/O error occurs when reading or writing
* @throws FileAlreadyExistsException
* if the target file exists but cannot be replaced because the
* {@code REPLACE_EXISTING} option is not specified (optional
* specific exception)
* @throws DirectoryNotEmptyException
* the {@code REPLACE_EXISTING} option is specified but the file
* cannot be replaced because it is a non-empty directory
* (optional specific exception) *
* @throws UnsupportedOperationException
* if {@code options} contains a copy option that is not supported
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkWrite(String) checkWrite}
* method is invoked to check write access to the file. Where the
* {@code REPLACE_EXISTING} option is specified, the security
* manager's {@link SecurityManager#checkDelete(String) checkDelete}
* method is invoked to check that an existing file can be deleted.
*/
public static long copy(InputStream in, Path target, CopyOption... options)
throws IOException
{
// ensure not null before opening file
Objects.requireNonNull(in);
// check for REPLACE_EXISTING
boolean replaceExisting = false;
for (CopyOption opt: options) {
if (opt == StandardCopyOption.REPLACE_EXISTING) {
replaceExisting = true;
} else {
if (opt == null) {
throw new NullPointerException("options contains 'null'");
} else {
throw new UnsupportedOperationException(opt + " not supported");
}
}
}
// attempt to delete an existing file
SecurityException se = null;
if (replaceExisting) {
try {
deleteIfExists(target);
} catch (SecurityException x) {
se = x;
}
}
// attempt to create target file. If it fails with
// FileAlreadyExistsException then it may be because the security
// manager prevented us from deleting the file, in which case we just
// throw the SecurityException.
OutputStream ostream;
try {
ostream = newOutputStream(target, StandardOpenOption.CREATE_NEW,
StandardOpenOption.WRITE);
} catch (FileAlreadyExistsException x) {
if (se != null)
throw se;
// someone else won the race and created the file
throw x;
}
// do the copy
try (OutputStream out = ostream) {
return copy(in, out);
}
}
/**
* Copies all bytes from a file to an output stream.
*
* If an I/O error occurs reading from the file or writing to the output
* stream, then it may do so after some bytes have been read or written.
* Consequently the output stream may be in an inconsistent state. It is
* strongly recommended that the output stream be promptly closed if an I/O
* error occurs.
*
*
This method may block indefinitely writing to the output stream (or
* reading from the file). The behavior for the case that the output stream
* is asynchronously closed or the thread interrupted during the copy
* is highly output stream and file system provider specific and therefore
* not specified.
*
*
Note that if the given output stream is {@link java.io.Flushable}
* then its {@link java.io.Flushable#flush flush} method may need to invoked
* after this method completes so as to flush any buffered output.
*
* @param source
* the path to the file
* @param out
* the output stream to write to
*
* @return the number of bytes read or written
*
* @throws IOException
* if an I/O error occurs when reading or writing
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkRead(String) checkRead}
* method is invoked to check read access to the file.
*/
public static long copy(Path source, OutputStream out) throws IOException {
// ensure not null before opening file
Objects.requireNonNull(out);
try (InputStream in = newInputStream(source)) {
return copy(in, out);
}
}
/**
* The maximum size of array to allocate.
* Some VMs reserve some header words in an array.
* Attempts to allocate larger arrays may result in
* OutOfMemoryError: Requested array size exceeds VM limit
*/
private static final int MAX_BUFFER_SIZE = Integer.MAX_VALUE - 8;
/**
* Reads all the bytes from an input stream. Uses {@code initialSize} as a hint
* about how many bytes the stream will have.
*
* @param source
* the input stream to read from
* @param initialSize
* the initial size of the byte array to allocate
*
* @return a byte array containing the bytes read from the file
*
* @throws IOException
* if an I/O error occurs reading from the stream
* @throws OutOfMemoryError
* if an array of the required size cannot be allocated
*/
private static byte[] read(InputStream source, int initialSize) throws IOException {
int capacity = initialSize;
byte[] buf = new byte[capacity];
int nread = 0;
int n;
for (;;) {
// read to EOF which may read more or less than initialSize (eg: file
// is truncated while we are reading)
while ((n = source.read(buf, nread, capacity - nread)) > 0)
nread += n;
// if last call to source.read() returned -1, we are done
// otherwise, try to read one more byte; if that failed we're done too
if (n < 0 || (n = source.read()) < 0)
break;
// one more byte was read; need to allocate a larger buffer
if (capacity <= MAX_BUFFER_SIZE - capacity) {
capacity = Math.max(capacity << 1, BUFFER_SIZE);
} else {
if (capacity == MAX_BUFFER_SIZE)
throw new OutOfMemoryError("Required array size too large");
capacity = MAX_BUFFER_SIZE;
}
buf = Arrays.copyOf(buf, capacity);
buf[nread++] = (byte)n;
}
return (capacity == nread) ? buf : Arrays.copyOf(buf, nread);
}
/**
* Reads all the bytes from a file. The method ensures that the file is
* closed when all bytes have been read or an I/O error, or other runtime
* exception, is thrown.
*
*
Note that this method is intended for simple cases where it is
* convenient to read all bytes into a byte array. It is not intended for
* reading in large files.
*
* @param path
* the path to the file
*
* @return a byte array containing the bytes read from the file
*
* @throws IOException
* if an I/O error occurs reading from the stream
* @throws OutOfMemoryError
* if an array of the required size cannot be allocated, for
* example the file is larger that {@code 2GB}
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkRead(String) checkRead}
* method is invoked to check read access to the file.
*/
public static byte[] readAllBytes(Path path) throws IOException {
try (SeekableByteChannel sbc = Files.newByteChannel(path);
InputStream in = Channels.newInputStream(sbc)) {
long size = sbc.size();
if (size > (long)MAX_BUFFER_SIZE)
throw new OutOfMemoryError("Required array size too large");
return read(in, (int)size);
}
}
/**
* Read all lines from a file. This method ensures that the file is
* closed when all bytes have been read or an I/O error, or other runtime
* exception, is thrown. Bytes from the file are decoded into characters
* using the specified charset.
*
*
This method recognizes the following as line terminators:
*
* -
\u000D followed by \u000A,
* CARRIAGE RETURN followed by LINE FEED
* -
\u000A, LINE FEED
* -
\u000D, CARRIAGE RETURN
*
* Additional Unicode line terminators may be recognized in future
* releases.
*
*
Note that this method is intended for simple cases where it is
* convenient to read all lines in a single operation. It is not intended
* for reading in large files.
*
* @param path
* the path to the file
* @param cs
* the charset to use for decoding
*
* @return the lines from the file as a {@code List}; whether the {@code
* List} is modifiable or not is implementation dependent and
* therefore not specified
*
* @throws IOException
* if an I/O error occurs reading from the file or a malformed or
* unmappable byte sequence is read
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkRead(String) checkRead}
* method is invoked to check read access to the file.
*
* @see #newBufferedReader
*/
public static List readAllLines(Path path, Charset cs) throws IOException {
try (BufferedReader reader = newBufferedReader(path, cs)) {
List result = new ArrayList<>();
for (;;) {
String line = reader.readLine();
if (line == null)
break;
result.add(line);
}
return result;
}
}
/**
* Read all lines from a file. Bytes from the file are decoded into characters
* using the {@link StandardCharsets#UTF_8 UTF-8} {@link Charset charset}.
*
* This method works as if invoking it were equivalent to evaluating the
* expression:
*
{@code
* Files.readAllLines(path, StandardCharsets.UTF_8)
* }
*
* @param path
* the path to the file
*
* @return the lines from the file as a {@code List}; whether the {@code
* List} is modifiable or not is implementation dependent and
* therefore not specified
*
* @throws IOException
* if an I/O error occurs reading from the file or a malformed or
* unmappable byte sequence is read
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkRead(String) checkRead}
* method is invoked to check read access to the file.
*
* @since 1.8
*/
public static List readAllLines(Path path) throws IOException {
return readAllLines(path, StandardCharsets.UTF_8);
}
/**
* Writes bytes to a file. The {@code options} parameter specifies how the
* the file is created or opened. If no options are present then this method
* works as if the {@link StandardOpenOption#CREATE CREATE}, {@link
* StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link
* StandardOpenOption#WRITE WRITE} options are present. In other words, it
* opens the file for writing, creating the file if it doesn't exist, or
* initially truncating an existing {@link #isRegularFile regular-file} to
* a size of {@code 0}. All bytes in the byte array are written to the file.
* The method ensures that the file is closed when all bytes have been
* written (or an I/O error or other runtime exception is thrown). If an I/O
* error occurs then it may do so after the file has created or truncated,
* or after some bytes have been written to the file.
*
* Usage example: By default the method creates a new file or
* overwrites an existing file. Suppose you instead want to append bytes
* to an existing file:
*
* Path path = ...
* byte[] bytes = ...
* Files.write(path, bytes, StandardOpenOption.APPEND);
*
*
* @param path
* the path to the file
* @param bytes
* the byte array with the bytes to write
* @param options
* options specifying how the file is opened
*
* @return the path
*
* @throws IOException
* if an I/O error occurs writing to or creating the file
* @throws UnsupportedOperationException
* if an unsupported option is specified
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkWrite(String) checkWrite}
* method is invoked to check write access to the file.
*/
public static Path write(Path path, byte[] bytes, OpenOption... options)
throws IOException
{
// ensure bytes is not null before opening file
Objects.requireNonNull(bytes);
try (OutputStream out = Files.newOutputStream(path, options)) {
int len = bytes.length;
int rem = len;
while (rem > 0) {
int n = Math.min(rem, BUFFER_SIZE);
out.write(bytes, (len-rem), n);
rem -= n;
}
}
return path;
}
/**
* Write lines of text to a file. Each line is a char sequence and is
* written to the file in sequence with each line terminated by the
* platform's line separator, as defined by the system property {@code
* line.separator}. Characters are encoded into bytes using the specified
* charset.
*
* The {@code options} parameter specifies how the the file is created
* or opened. If no options are present then this method works as if the
* {@link StandardOpenOption#CREATE CREATE}, {@link
* StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link
* StandardOpenOption#WRITE WRITE} options are present. In other words, it
* opens the file for writing, creating the file if it doesn't exist, or
* initially truncating an existing {@link #isRegularFile regular-file} to
* a size of {@code 0}. The method ensures that the file is closed when all
* lines have been written (or an I/O error or other runtime exception is
* thrown). If an I/O error occurs then it may do so after the file has
* created or truncated, or after some bytes have been written to the file.
*
* @param path
* the path to the file
* @param lines
* an object to iterate over the char sequences
* @param cs
* the charset to use for encoding
* @param options
* options specifying how the file is opened
*
* @return the path
*
* @throws IOException
* if an I/O error occurs writing to or creating the file, or the
* text cannot be encoded using the specified charset
* @throws UnsupportedOperationException
* if an unsupported option is specified
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkWrite(String) checkWrite}
* method is invoked to check write access to the file.
*/
public static Path write(Path path, Iterable lines,
Charset cs, OpenOption... options)
throws IOException
{
// ensure lines is not null before opening file
Objects.requireNonNull(lines);
CharsetEncoder encoder = cs.newEncoder();
OutputStream out = newOutputStream(path, options);
try (BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(out, encoder))) {
for (CharSequence line: lines) {
writer.append(line);
writer.newLine();
}
}
return path;
}
/**
* Write lines of text to a file. Characters are encoded into bytes using
* the {@link StandardCharsets#UTF_8 UTF-8} {@link Charset charset}.
*
*
This method works as if invoking it were equivalent to evaluating the
* expression:
*
{@code
* Files.write(path, lines, StandardCharsets.UTF_8, options);
* }
*
* @param path
* the path to the file
* @param lines
* an object to iterate over the char sequences
* @param options
* options specifying how the file is opened
*
* @return the path
*
* @throws IOException
* if an I/O error occurs writing to or creating the file, or the
* text cannot be encoded as {@code UTF-8}
* @throws UnsupportedOperationException
* if an unsupported option is specified
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkWrite(String) checkWrite}
* method is invoked to check write access to the file.
*
* @since 1.8
*/
public static Path write(Path path,
Iterable lines,
OpenOption... options)
throws IOException
{
return write(path, lines, StandardCharsets.UTF_8, options);
}
// -- Stream APIs --
/**
* Return a lazily populated {@code Stream}, the elements of
* which are the entries in the directory. The listing is not recursive.
*
* The elements of the stream are {@link Path} objects that are
* obtained as if by {@link Path#resolve(Path) resolving} the name of the
* directory entry against {@code dir}. Some file systems maintain special
* links to the directory itself and the directory's parent directory.
* Entries representing these links are not included.
*
*
The stream is weakly consistent. It is thread safe but does
* not freeze the directory while iterating, so it may (or may not)
* reflect updates to the directory that occur after returning from this
* method.
*
*
The returned stream encapsulates a {@link DirectoryStream}.
* If timely disposal of file system resources is required, the
* {@code try}-with-resources construct should be used to ensure that the
* stream's {@link Stream#close close} method is invoked after the stream
* operations are completed.
*
*
Operating on a closed stream behaves as if the end of stream
* has been reached. Due to read-ahead, one or more elements may be
* returned after the stream has been closed.
*
*
If an {@link IOException} is thrown when accessing the directory
* after this method has returned, it is wrapped in an {@link
* UncheckedIOException} which will be thrown from the method that caused
* the access to take place.
*
* @param dir The path to the directory
*
* @return The {@code Stream} describing the content of the
* directory
*
* @throws NotDirectoryException
* if the file could not otherwise be opened because it is not
* a directory (optional specific exception)
* @throws IOException
* if an I/O error occurs when opening the directory
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkRead(String) checkRead}
* method is invoked to check read access to the directory.
*
* @see #newDirectoryStream(Path)
* @since 1.8
*/
public static Stream list(Path dir) throws IOException {
DirectoryStream ds = Files.newDirectoryStream(dir);
try {
final Iterator delegate = ds.iterator();
// Re-wrap DirectoryIteratorException to UncheckedIOException
Iterator it = new Iterator() {
@Override
public boolean hasNext() {
try {
return delegate.hasNext();
} catch (DirectoryIteratorException e) {
throw new UncheckedIOException(e.getCause());
}
}
@Override
public Path next() {
try {
return delegate.next();
} catch (DirectoryIteratorException e) {
throw new UncheckedIOException(e.getCause());
}
}
};
return StreamSupport.stream(Spliterators.spliteratorUnknownSize(it, Spliterator.DISTINCT), false)
.onClose(asUncheckedRunnable(ds));
} catch (Error|RuntimeException e) {
try {
ds.close();
} catch (IOException ex) {
try {
e.addSuppressed(ex);
} catch (Throwable ignore) {}
}
throw e;
}
}
/**
* Return a {@code Stream} that is lazily populated with {@code
* Path} by walking the file tree rooted at a given starting file. The
* file tree is traversed depth-first, the elements in the stream
* are {@link Path} objects that are obtained as if by {@link
* Path#resolve(Path) resolving} the relative path against {@code start}.
*
* The {@code stream} walks the file tree as elements are consumed.
* The {@code Stream} returned is guaranteed to have at least one
* element, the starting file itself. For each file visited, the stream
* attempts to read its {@link BasicFileAttributes}. If the file is a
* directory and can be opened successfully, entries in the directory, and
* their descendants will follow the directory in the stream as
* they are encountered. When all entries have been visited, then the
* directory is closed. The file tree walk then continues at the next
* sibling of the directory.
*
*
The stream is weakly consistent. It does not freeze the
* file tree while iterating, so it may (or may not) reflect updates to
* the file tree that occur after returned from this method.
*
*
By default, symbolic links are not automatically followed by this
* method. If the {@code options} parameter contains the {@link
* FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then symbolic links are
* followed. When following links, and the attributes of the target cannot
* be read, then this method attempts to get the {@code BasicFileAttributes}
* of the link.
*
*
If the {@code options} parameter contains the {@link
* FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then the stream keeps
* track of directories visited so that cycles can be detected. A cycle
* arises when there is an entry in a directory that is an ancestor of the
* directory. Cycle detection is done by recording the {@link
* java.nio.file.attribute.BasicFileAttributes#fileKey file-key} of directories,
* or if file keys are not available, by invoking the {@link #isSameFile
* isSameFile} method to test if a directory is the same file as an
* ancestor. When a cycle is detected it is treated as an I/O error with
* an instance of {@link FileSystemLoopException}.
*
*
The {@code maxDepth} parameter is the maximum number of levels of
* directories to visit. A value of {@code 0} means that only the starting
* file is visited, unless denied by the security manager. A value of
* {@link Integer#MAX_VALUE MAX_VALUE} may be used to indicate that all
* levels should be visited.
*
*
When a security manager is installed and it denies access to a file
* (or directory), then it is ignored and not included in the stream.
*
*
The returned stream encapsulates one or more {@link DirectoryStream}s.
* If timely disposal of file system resources is required, the
* {@code try}-with-resources construct should be used to ensure that the
* stream's {@link Stream#close close} method is invoked after the stream
* operations are completed. Operating on a closed stream will result in an
* {@link java.lang.IllegalStateException}.
*
*
If an {@link IOException} is thrown when accessing the directory
* after this method has returned, it is wrapped in an {@link
* UncheckedIOException} which will be thrown from the method that caused
* the access to take place.
*
* @param start
* the starting file
* @param maxDepth
* the maximum number of directory levels to visit
* @param options
* options to configure the traversal
*
* @return the {@link Stream} of {@link Path}
*
* @throws IllegalArgumentException
* if the {@code maxDepth} parameter is negative
* @throws SecurityException
* If the security manager denies access to the starting file.
* In the case of the default provider, the {@link
* SecurityManager#checkRead(String) checkRead} method is invoked
* to check read access to the directory.
* @throws IOException
* if an I/O error is thrown when accessing the starting file.
* @since 1.8
*/
public static Stream walk(Path start,
int maxDepth,
FileVisitOption... options)
throws IOException
{
FileTreeIterator iterator = new FileTreeIterator(start, maxDepth, options);
try {
return StreamSupport.stream(Spliterators.spliteratorUnknownSize(iterator, Spliterator.DISTINCT), false)
.onClose(iterator::close)
.map(entry -> entry.file());
} catch (Error|RuntimeException e) {
iterator.close();
throw e;
}
}
/**
* Return a {@code Stream} that is lazily populated with {@code
* Path} by walking the file tree rooted at a given starting file. The
* file tree is traversed depth-first, the elements in the stream
* are {@link Path} objects that are obtained as if by {@link
* Path#resolve(Path) resolving} the relative path against {@code start}.
*
* This method works as if invoking it were equivalent to evaluating the
* expression:
*
* walk(start, Integer.MAX_VALUE, options)
*
* In other words, it visits all levels of the file tree.
*
* The returned stream encapsulates one or more {@link DirectoryStream}s.
* If timely disposal of file system resources is required, the
* {@code try}-with-resources construct should be used to ensure that the
* stream's {@link Stream#close close} method is invoked after the stream
* operations are completed. Operating on a closed stream will result in an
* {@link java.lang.IllegalStateException}.
*
* @param start
* the starting file
* @param options
* options to configure the traversal
*
* @return the {@link Stream} of {@link Path}
*
* @throws SecurityException
* If the security manager denies access to the starting file.
* In the case of the default provider, the {@link
* SecurityManager#checkRead(String) checkRead} method is invoked
* to check read access to the directory.
* @throws IOException
* if an I/O error is thrown when accessing the starting file.
*
* @see #walk(Path, int, FileVisitOption...)
* @since 1.8
*/
public static Stream walk(Path start, FileVisitOption... options) throws IOException {
return walk(start, Integer.MAX_VALUE, options);
}
/**
* Return a {@code Stream} that is lazily populated with {@code
* Path} by searching for files in a file tree rooted at a given starting
* file.
*
* This method walks the file tree in exactly the manner specified by
* the {@link #walk walk} method. For each file encountered, the given
* {@link BiPredicate} is invoked with its {@link Path} and {@link
* BasicFileAttributes}. The {@code Path} object is obtained as if by
* {@link Path#resolve(Path) resolving} the relative path against {@code
* start} and is only included in the returned {@link Stream} if
* the {@code BiPredicate} returns true. Compare to calling {@link
* java.util.stream.Stream#filter filter} on the {@code Stream}
* returned by {@code walk} method, this method may be more efficient by
* avoiding redundant retrieval of the {@code BasicFileAttributes}.
*
*
The returned stream encapsulates one or more {@link DirectoryStream}s.
* If timely disposal of file system resources is required, the
* {@code try}-with-resources construct should be used to ensure that the
* stream's {@link Stream#close close} method is invoked after the stream
* operations are completed. Operating on a closed stream will result in an
* {@link java.lang.IllegalStateException}.
*
*
If an {@link IOException} is thrown when accessing the directory
* after returned from this method, it is wrapped in an {@link
* UncheckedIOException} which will be thrown from the method that caused
* the access to take place.
*
* @param start
* the starting file
* @param maxDepth
* the maximum number of directory levels to search
* @param matcher
* the function used to decide whether a file should be included
* in the returned stream
* @param options
* options to configure the traversal
*
* @return the {@link Stream} of {@link Path}
*
* @throws IllegalArgumentException
* if the {@code maxDepth} parameter is negative
* @throws SecurityException
* If the security manager denies access to the starting file.
* In the case of the default provider, the {@link
* SecurityManager#checkRead(String) checkRead} method is invoked
* to check read access to the directory.
* @throws IOException
* if an I/O error is thrown when accessing the starting file.
*
* @see #walk(Path, int, FileVisitOption...)
* @since 1.8
*/
public static Stream find(Path start,
int maxDepth,
BiPredicate matcher,
FileVisitOption... options)
throws IOException
{
FileTreeIterator iterator = new FileTreeIterator(start, maxDepth, options);
try {
return StreamSupport.stream(Spliterators.spliteratorUnknownSize(iterator, Spliterator.DISTINCT), false)
.onClose(iterator::close)
.filter(entry -> matcher.test(entry.file(), entry.attributes()))
.map(entry -> entry.file());
} catch (Error|RuntimeException e) {
iterator.close();
throw e;
}
}
/**
* Read all lines from a file as a {@code Stream}. Unlike {@link
* #readAllLines(Path, Charset) readAllLines}, this method does not read
* all lines into a {@code List}, but instead populates lazily as the stream
* is consumed.
*
* Bytes from the file are decoded into characters using the specified
* charset and the same line terminators as specified by {@code
* readAllLines} are supported.
*
*
After this method returns, then any subsequent I/O exception that
* occurs while reading from the file or when a malformed or unmappable byte
* sequence is read, is wrapped in an {@link UncheckedIOException} that will
* be thrown from the
* {@link java.util.stream.Stream} method that caused the read to take
* place. In case an {@code IOException} is thrown when closing the file,
* it is also wrapped as an {@code UncheckedIOException}.
*
*
The returned stream encapsulates a {@link Reader}. If timely
* disposal of file system resources is required, the try-with-resources
* construct should be used to ensure that the stream's
* {@link Stream#close close} method is invoked after the stream operations
* are completed.
*
*
* @param path
* the path to the file
* @param cs
* the charset to use for decoding
*
* @return the lines from the file as a {@code Stream}
*
* @throws IOException
* if an I/O error occurs opening the file
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkRead(String) checkRead}
* method is invoked to check read access to the file.
*
* @see #readAllLines(Path, Charset)
* @see #newBufferedReader(Path, Charset)
* @see java.io.BufferedReader#lines()
* @since 1.8
*/
public static Stream lines(Path path, Charset cs) throws IOException {
BufferedReader br = Files.newBufferedReader(path, cs);
try {
return br.lines().onClose(asUncheckedRunnable(br));
} catch (Error|RuntimeException e) {
try {
br.close();
} catch (IOException ex) {
try {
e.addSuppressed(ex);
} catch (Throwable ignore) {}
}
throw e;
}
}
/**
* Read all lines from a file as a {@code Stream}. Bytes from the file are
* decoded into characters using the {@link StandardCharsets#UTF_8 UTF-8}
* {@link Charset charset}.
*
* This method works as if invoking it were equivalent to evaluating the
* expression:
*
{@code
* Files.lines(path, StandardCharsets.UTF_8)
* }
*
* @param path
* the path to the file
*
* @return the lines from the file as a {@code Stream}
*
* @throws IOException
* if an I/O error occurs opening the file
* @throws SecurityException
* In the case of the default provider, and a security manager is
* installed, the {@link SecurityManager#checkRead(String) checkRead}
* method is invoked to check read access to the file.
*
* @since 1.8
*/
public static Stream lines(Path path) throws IOException {
return lines(path, StandardCharsets.UTF_8);
}
}