java.io.RandomAccessFile Maven / Gradle / Ivy
/*
This is not an official specification document, and usage is restricted.
NOTICE
(c) 2005-2007 Sun Microsystems, Inc. All Rights Reserved.
Neither this file nor any files generated from it describe a complete
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example, no permission is given for you to incorporate this file, in
whole or in part, in an implementation of a Java specification.
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documentation, such as a unified set of documents of API signatures for
a platform that includes technologies expressed as Java APIs. The file
may also be used to produce "compilation stubs," which allow
applications to be compiled and validated for such platforms.
Any work generated from this file, such as unified javadocs or compiled
stub files, must be accompanied by this notice in its entirety.
This work corresponds to the API signatures of JSR 219: Foundation
Profile 1.1. In the event of a discrepency between this work and the
JSR 219 specification, which is available at
http://www.jcp.org/en/jsr/detail?id=219, the latter takes precedence.
*/
package java.io;
/**
* Instances of this class support both reading and writing to a
* random access file. A random access file behaves like a large
* array of bytes stored in the file system. There is a kind of cursor,
* or index into the implied array, called the file pointer;
* input operations read bytes starting at the file pointer and advance
* the file pointer past the bytes read. If the random access file is
* created in read/write mode, then output operations are also available;
* output operations write bytes starting at the file pointer and advance
* the file pointer past the bytes written. Output operations that write
* past the current end of the implied array cause the array to be
* extended. The file pointer can be read by the
* getFilePointer method and set by the seek
* method.
*
* It is generally true of all the reading routines in this class that
* if end-of-file is reached before the desired number of bytes has been
* read, an EOFException (which is a kind of
* IOException) is thrown. If any byte cannot be read for
* any reason other than end-of-file, an IOException other
* than EOFException is thrown. In particular, an
* IOException may be thrown if the stream has been closed.
*
* @author unascribed
* @version 1.57, 05/03/00
* @since JDK1.0
*/
public class RandomAccessFile implements DataOutput, DataInput
{
/**
* Creates a random access file stream to read from, and optionally
* to write to, a file with the specified name. A new
* {@link FileDescriptor} object is created to represent the
* connection to the file.
*
*
The mode argument specifies the access mode with which the
* file is to be opened. The permitted values and their meanings are as
* specified for the RandomAccessFile(File,String) constructor.
*
*
* If there is a security manager, its checkRead method
* is called with the name argument
* as its argument to see if read access to the file is allowed.
* If the mode allows writing, the security manager's
* checkWrite method
* is also called with the name argument
* as its argument to see if write access to the file is allowed.
*
* @param name the system-dependent filename
* @param mode the access mode
* @exception IllegalArgumentException if the mode argument is not equal
* to one of "r", "rw", "rws", or
* "rwd"
* @exception FileNotFoundException if the file exists but is a directory
* rather than a regular file, or cannot be opened or
* created for any other reason
* @exception SecurityException if a security manager exists and its
* checkRead method denies read access to the file
* or the mode is "rw" and the security manager's
* checkWrite method denies write access to the file
* @see java.lang.SecurityException
* @see java.lang.SecurityManager#checkRead(java.lang.String)
* @see java.lang.SecurityManager#checkWrite(java.lang.String)
* @revised 1.4
* @spec JSR-51
*/
public RandomAccessFile(String name, String mode)
throws FileNotFoundException
{ }
/**
* Creates a random access file stream to read from, and optionally to
* write to, the file specified by the {@link File} argument. A new {@link
* FileDescriptor} object is created to represent this file connection.
*
* The mode argument specifies the access mode
* in which the file is to be opened. The permitted values and their
* meanings are:
*
*
* Value
Meaning
"r"
* Open for reading only. Invoking any of the write
* methods of the resulting object will cause an {@link
* java.io.IOException} to be thrown. "rw"
* Open for reading and writing. If the file does not already
* exist then an attempt will be made to create it. "rws"
* Open for reading and writing, as with "rw", and also
* require that every update to the file's content or metadata be
* written synchronously to the underlying storage device. "rwd"
* Open for reading and writing, as with "rw", and also
* require that every update to the file's content be written
* synchronously to the underlying storage device.
*
* If
* the file resides on a local storage device then when an invocation of a
* method of this class returns it is guaranteed that all changes made to
* the file by that invocation will have been written to that device. This
* is useful for ensuring that critical information is not lost in the
* event of a system crash. If the file does not reside on a local device
* then no such guarantee is made.
*
* The "rwd" mode can be used to reduce the number of I/O
* operations performed. Using "rwd" only requires updates to the
* file's content to be written to storage; using "rws" requires
* updates to both the file's content and its metadata to be written, which
* generally requires at least one more low-level I/O operation.
*
*
If there is a security manager, its checkRead method is
* called with the pathname of the file argument as its
* argument to see if read access to the file is allowed. If the mode
* allows writing, the security manager's checkWrite method is
* also called with the path argument to see if write access to the file is
* allowed.
*
* @param file the file object
* @param mode the access mode, as described
* above
* @exception IllegalArgumentException if the mode argument is not equal
* to one of "r", "rw", "rws", or
* "rwd"
* @exception FileNotFoundException if the file exists but is a directory
* rather than a regular file, or cannot be opened or
* created for any other reason
* @exception SecurityException if a security manager exists and its
* checkRead method denies read access to the file
* or the mode is "rw" and the security manager's
* checkWrite method denies write access to the file
* @see java.lang.SecurityManager#checkRead(java.lang.String)
* @see java.lang.SecurityManager#checkWrite(java.lang.String)
* @revised 1.4
* @spec JSR-51
*/
public RandomAccessFile(File file, String mode) throws FileNotFoundException
{ }
/**
* Returns the opaque file descriptor object associated with this
* stream.
*
* @return the file descriptor object associated with this stream.
* @exception IOException if an I/O error occurs.
* @see java.io.FileDescriptor
*/
public final FileDescriptor getFD() throws IOException {
return null;
}
/**
* Reads a byte of data from this file. The byte is returned as an
* integer in the range 0 to 255 (0x00-0x0ff). This
* method blocks if no input is yet available.
*
* Although RandomAccessFile is not a subclass of
* InputStream, this method behaves in exactly the same
* way as the {@link InputStream#read()} method of
* InputStream.
*
* @return the next byte of data, or -1 if the end of the
* file has been reached.
* @exception IOException if an I/O error occurs. Not thrown if
* end-of-file has been reached.
*/
public int read() throws IOException {
return 0;
}
/**
* Reads up to len bytes of data from this file into an
* array of bytes. This method blocks until at least one byte of input
* is available.
*
* Although RandomAccessFile is not a subclass of
* InputStream, this method behaves in the exactly the
* same way as the {@link InputStream#read(byte[], int, int)} method of
* InputStream.
*
* @param b the buffer into which the data is read.
* @param off the start offset of the data.
* @param len the maximum number of bytes read.
* @return the total number of bytes read into the buffer, or
* -1 if there is no more data because the end of
* the file has been reached.
* @exception IOException if an I/O error occurs.
*/
public int read(byte[] b, int off, int len) throws IOException {
return 0;
}
/**
* Reads up to b.length bytes of data from this file
* into an array of bytes. This method blocks until at least one byte
* of input is available.
*
* Although RandomAccessFile is not a subclass of
* InputStream, this method behaves in the exactly the
* same way as the {@link InputStream#read(byte[])} method of
* InputStream.
*
* @param b the buffer into which the data is read.
* @return the total number of bytes read into the buffer, or
* -1 if there is no more data because the end of
* this file has been reached.
* @exception IOException if an I/O error occurs.
*/
public int read(byte[] b) throws IOException {
return 0;
}
/**
* Reads b.length bytes from this file into the byte
* array, starting at the current file pointer. This method reads
* repeatedly from the file until the requested number of bytes are
* read. This method blocks until the requested number of bytes are
* read, the end of the stream is detected, or an exception is thrown.
*
* @param b the buffer into which the data is read.
* @exception EOFException if this file reaches the end before reading
* all the bytes.
* @exception IOException if an I/O error occurs.
*/
public final void readFully(byte[] b) throws IOException { }
/**
* Reads exactly len bytes from this file into the byte
* array, starting at the current file pointer. This method reads
* repeatedly from the file until the requested number of bytes are
* read. This method blocks until the requested number of bytes are
* read, the end of the stream is detected, or an exception is thrown.
*
* @param b the buffer into which the data is read.
* @param off the start offset of the data.
* @param len the number of bytes to read.
* @exception EOFException if this file reaches the end before reading
* all the bytes.
* @exception IOException if an I/O error occurs.
*/
public final void readFully(byte[] b, int off, int len) throws IOException
{ }
/**
* Attempts to skip over n bytes of input discarding the
* skipped bytes.
*
*
* This method may skip over some smaller number of bytes, possibly zero.
* This may result from any of a number of conditions; reaching end of
* file before n bytes have been skipped is only one
* possibility. This method never throws an EOFException.
* The actual number of bytes skipped is returned. If n
* is negative, no bytes are skipped.
*
* @param n the number of bytes to be skipped.
* @return the actual number of bytes skipped.
* @exception IOException if an I/O error occurs.
*/
public int skipBytes(int n) throws IOException {
return 0;
}
/**
* Writes the specified byte to this file. The write starts at
* the current file pointer.
*
* @param b the byte to be written.
* @exception IOException if an I/O error occurs.
*/
public void write(int b) throws IOException { }
/**
* Writes b.length bytes from the specified byte array
* to this file, starting at the current file pointer.
*
* @param b the data.
* @exception IOException if an I/O error occurs.
*/
public void write(byte[] b) throws IOException { }
/**
* Writes len bytes from the specified byte array
* starting at offset off to this file.
*
* @param b the data.
* @param off the start offset in the data.
* @param len the number of bytes to write.
* @exception IOException if an I/O error occurs.
*/
public void write(byte[] b, int off, int len) throws IOException { }
/**
* Returns the current offset in this file.
*
* @return the offset from the beginning of the file, in bytes,
* at which the next read or write occurs.
* @exception IOException if an I/O error occurs.
*/
public long getFilePointer() throws IOException {
return -1;
}
/**
* Sets the file-pointer offset, measured from the beginning of this
* file, at which the next read or write occurs. The offset may be
* set beyond the end of the file. Setting the offset beyond the end
* of the file does not change the file length. The file length will
* change only by writing after the offset has been set beyond the end
* of the file.
*
* @param pos the offset position, measured in bytes from the
* beginning of the file, at which to set the file
* pointer.
* @exception IOException if pos is less than
* 0 or if an I/O error occurs.
*/
public void seek(long pos) throws IOException { }
/**
* Returns the length of this file.
*
* @return the length of this file, measured in bytes.
* @exception IOException if an I/O error occurs.
*/
public long length() throws IOException {
return -1;
}
/**
* Sets the length of this file.
*
*
If the present length of the file as returned by the
* length method is greater than the newLength
* argument then the file will be truncated. In this case, if the file
* offset as returned by the getFilePointer method is greater
* then newLength then after this method returns the offset
* will be equal to newLength.
*
*
If the present length of the file as returned by the
* length method is smaller than the newLength
* argument then the file will be extended. In this case, the contents of
* the extended portion of the file are not defined.
*
* @param newLength The desired length of the file
* @exception IOException If an I/O error occurs
* @since 1.2
*/
public void setLength(long newLength) throws IOException { }
/**
* Closes this random access file stream and releases any system
* resources associated with the stream. A closed random access
* file cannot perform input or output operations and cannot be
* reopened.
*
* @exception IOException if an I/O error occurs.
*
* @revised 1.4
* @spec JSR-51
*/
public void close() throws IOException { }
/**
* Reads a boolean from this file. This method reads a
* single byte from the file, starting at the current file pointer.
* A value of 0 represents
* false. Any other value represents true.
* This method blocks until the byte is read, the end of the stream
* is detected, or an exception is thrown.
*
* @return the boolean value read.
* @exception EOFException if this file has reached the end.
* @exception IOException if an I/O error occurs.
*/
public final boolean readBoolean() throws IOException {
return false;
}
/**
* Reads a signed eight-bit value from this file. This method reads a
* byte from the file, starting from the current file pointer.
* If the byte read is b, where
* 0 <= b <= 255,
* then the result is:
*
* (byte)(b)
*
*
* This method blocks until the byte is read, the end of the stream
* is detected, or an exception is thrown.
*
* @return the next byte of this file as a signed eight-bit
* byte.
* @exception EOFException if this file has reached the end.
* @exception IOException if an I/O error occurs.
*/
public final byte readByte() throws IOException {
return ' ';
}
/**
* Reads an unsigned eight-bit number from this file. This method reads
* a byte from this file, starting at the current file pointer,
* and returns that byte.
*
* This method blocks until the byte is read, the end of the stream
* is detected, or an exception is thrown.
*
* @return the next byte of this file, interpreted as an unsigned
* eight-bit number.
* @exception EOFException if this file has reached the end.
* @exception IOException if an I/O error occurs.
*/
public final int readUnsignedByte() throws IOException {
return 0;
}
/**
* Reads a signed 16-bit number from this file. The method reads two
* bytes from this file, starting at the current file pointer.
* If the two bytes read, in order, are
* b1 and b2, where each of the two values is
* between 0 and 255, inclusive, then the
* result is equal to:
*
* (short)((b1 << 8) | b2)
*
*
* This method blocks until the two bytes are read, the end of the
* stream is detected, or an exception is thrown.
*
* @return the next two bytes of this file, interpreted as a signed
* 16-bit number.
* @exception EOFException if this file reaches the end before reading
* two bytes.
* @exception IOException if an I/O error occurs.
*/
public final short readShort() throws IOException {
return -1;
}
/**
* Reads an unsigned 16-bit number from this file. This method reads
* two bytes from the file, starting at the current file pointer.
* If the bytes read, in order, are
* b1 and b2, where
* 0 <= b1, b2 <= 255,
* then the result is equal to:
*
* (b1 << 8) | b2
*
*
* This method blocks until the two bytes are read, the end of the
* stream is detected, or an exception is thrown.
*
* @return the next two bytes of this file, interpreted as an unsigned
* 16-bit integer.
* @exception EOFException if this file reaches the end before reading
* two bytes.
* @exception IOException if an I/O error occurs.
*/
public final int readUnsignedShort() throws IOException {
return 0;
}
/**
* Reads a Unicode character from this file. This method reads two
* bytes from the file, starting at the current file pointer.
* If the bytes read, in order, are
* b1 and b2, where
* 0 <= b1, b2 <= 255,
* then the result is equal to:
*
* (char)((b1 << 8) | b2)
*
*
* This method blocks until the two bytes are read, the end of the
* stream is detected, or an exception is thrown.
*
* @return the next two bytes of this file as a Unicode character.
* @exception EOFException if this file reaches the end before reading
* two bytes.
* @exception IOException if an I/O error occurs.
*/
public final char readChar() throws IOException {
return ' ';
}
/**
* Reads a signed 32-bit integer from this file. This method reads 4
* bytes from the file, starting at the current file pointer.
* If the bytes read, in order, are b1,
* b2, b3, and b4, where
* 0 <= b1, b2, b3, b4 <= 255,
* then the result is equal to:
*
* (b1 << 24) | (b2 << 16) + (b3 << 8) + b4
*
*
* This method blocks until the four bytes are read, the end of the
* stream is detected, or an exception is thrown.
*
* @return the next four bytes of this file, interpreted as an
* int.
* @exception EOFException if this file reaches the end before reading
* four bytes.
* @exception IOException if an I/O error occurs.
*/
public final int readInt() throws IOException {
return 0;
}
/**
* Reads a signed 64-bit integer from this file. This method reads eight
* bytes from the file, starting at the current file pointer.
* If the bytes read, in order, are
* b1, b2, b3,
* b4, b5, b6,
* b7, and b8, where:
*
* 0 <= b1, b2, b3, b4, b5, b6, b7, b8 <=255,
*
*
* then the result is equal to:
*
* ((long)b1 << 56) + ((long)b2 << 48)
* + ((long)b3 << 40) + ((long)b4 << 32)
* + ((long)b5 << 24) + ((long)b6 << 16)
* + ((long)b7 << 8) + b8
*
*
* This method blocks until the eight bytes are read, the end of the
* stream is detected, or an exception is thrown.
*
* @return the next eight bytes of this file, interpreted as a
* long.
* @exception EOFException if this file reaches the end before reading
* eight bytes.
* @exception IOException if an I/O error occurs.
*/
public final long readLong() throws IOException {
return -1;
}
/**
* Reads a float from this file. This method reads an
* int value, starting at the current file pointer,
* as if by the readInt method
* and then converts that int to a float
* using the intBitsToFloat method in class
* Float.
*
* This method blocks until the four bytes are read, the end of the
* stream is detected, or an exception is thrown.
*
* @return the next four bytes of this file, interpreted as a
* float.
* @exception EOFException if this file reaches the end before reading
* four bytes.
* @exception IOException if an I/O error occurs.
* @see java.io.RandomAccessFile#readInt()
* @see java.lang.Float#intBitsToFloat(int)
*/
public final float readFloat() throws IOException {
return 0.0f;
}
/**
* Reads a double from this file. This method reads a
* long value, starting at the current file pointer,
* as if by the readLong method
* and then converts that long to a double
* using the longBitsToDouble method in
* class Double.
*
* This method blocks until the eight bytes are read, the end of the
* stream is detected, or an exception is thrown.
*
* @return the next eight bytes of this file, interpreted as a
* double.
* @exception EOFException if this file reaches the end before reading
* eight bytes.
* @exception IOException if an I/O error occurs.
* @see java.io.RandomAccessFile#readLong()
* @see java.lang.Double#longBitsToDouble(long)
*/
public final double readDouble() throws IOException {
return 0.0d;
}
/**
* Reads the next line of text from this file. This method successively
* reads bytes from the file, starting at the current file pointer,
* until it reaches a line terminator or the end
* of the file. Each byte is converted into a character by taking the
* byte's value for the lower eight bits of the character and setting the
* high eight bits of the character to zero. This method does not,
* therefore, support the full Unicode character set.
*
*
A line of text is terminated by a carriage-return character
* ('\r'), a newline character ('\n'), a
* carriage-return character immediately followed by a newline character,
* or the end of the file. Line-terminating characters are discarded and
* are not included as part of the string returned.
*
*
This method blocks until a newline character is read, a carriage
* return and the byte following it are read (to see if it is a newline),
* the end of the file is reached, or an exception is thrown.
*
* @return the next line of text from this file, or null if end
* of file is encountered before even one byte is read.
* @exception IOException if an I/O error occurs.
*/
public final String readLine() throws IOException {
return null;
}
/**
* Reads in a string from this file. The string has been encoded
* using a modified UTF-8 format.
*
* The first two bytes are read, starting from the current file
* pointer, as if by
* readUnsignedShort. This value gives the number of
* following bytes that are in the encoded string, not
* the length of the resulting string. The following bytes are then
* interpreted as bytes encoding characters in the UTF-8 format
* and are converted into characters.
*
* This method blocks until all the bytes are read, the end of the
* stream is detected, or an exception is thrown.
*
* @return a Unicode string.
* @exception EOFException if this file reaches the end before
* reading all the bytes.
* @exception IOException if an I/O error occurs.
* @exception UTFDataFormatException if the bytes do not represent
* valid UTF-8 encoding of a Unicode string.
* @see java.io.RandomAccessFile#readUnsignedShort()
*/
public final String readUTF() throws IOException {
return null;
}
/**
* Writes a boolean to the file as a one-byte value. The
* value true is written out as the value
* (byte)1; the value false is written out
* as the value (byte)0. The write starts at
* the current position of the file pointer.
*
* @param v a boolean value to be written.
* @exception IOException if an I/O error occurs.
*/
public final void writeBoolean(boolean v) throws IOException { }
/**
* Writes a byte to the file as a one-byte value. The
* write starts at the current position of the file pointer.
*
* @param v a byte value to be written.
* @exception IOException if an I/O error occurs.
*/
public final void writeByte(int v) throws IOException { }
/**
* Writes a short to the file as two bytes, high byte first.
* The write starts at the current position of the file pointer.
*
* @param v a short to be written.
* @exception IOException if an I/O error occurs.
*/
public final void writeShort(int v) throws IOException { }
/**
* Writes a char to the file as a two-byte value, high
* byte first. The write starts at the current position of the
* file pointer.
*
* @param v a char value to be written.
* @exception IOException if an I/O error occurs.
*/
public final void writeChar(int v) throws IOException { }
/**
* Writes an int to the file as four bytes, high byte first.
* The write starts at the current position of the file pointer.
*
* @param v an int to be written.
* @exception IOException if an I/O error occurs.
*/
public final void writeInt(int v) throws IOException { }
/**
* Writes a long to the file as eight bytes, high byte first.
* The write starts at the current position of the file pointer.
*
* @param v a long to be written.
* @exception IOException if an I/O error occurs.
*/
public final void writeLong(long v) throws IOException { }
/**
* Converts the float argument to an int using the
* floatToIntBits method in class Float,
* and then writes that int value to the file as a
* four-byte quantity, high byte first. The write starts at the
* current position of the file pointer.
*
* @param v a float value to be written.
* @exception IOException if an I/O error occurs.
* @see java.lang.Float#floatToIntBits(float)
*/
public final void writeFloat(float v) throws IOException { }
/**
* Converts the double argument to a long using the
* doubleToLongBits method in class Double,
* and then writes that long value to the file as an
* eight-byte quantity, high byte first. The write starts at the current
* position of the file pointer.
*
* @param v a double value to be written.
* @exception IOException if an I/O error occurs.
* @see java.lang.Double#doubleToLongBits(double)
*/
public final void writeDouble(double v) throws IOException { }
/**
* Writes the string to the file as a sequence of bytes. Each
* character in the string is written out, in sequence, by discarding
* its high eight bits. The write starts at the current position of
* the file pointer.
*
* @param s a string of bytes to be written.
* @exception IOException if an I/O error occurs.
*/
public final void writeBytes(String s) throws IOException { }
/**
* Writes a string to the file as a sequence of characters. Each
* character is written to the data output stream as if by the
* writeChar method. The write starts at the current
* position of the file pointer.
*
* @param s a String value to be written.
* @exception IOException if an I/O error occurs.
* @see java.io.RandomAccessFile#writeChar(int)
*/
public final void writeChars(String s) throws IOException { }
/**
* Writes a string to the file using UTF-8 encoding in a
* machine-independent manner.
*
* First, two bytes are written to the file, starting at the
* current file pointer, as if by the
* writeShort method giving the number of bytes to
* follow. This value is the number of bytes actually written out,
* not the length of the string. Following the length, each character
* of the string is output, in sequence, using the UTF-8 encoding
* for each character.
*
* @param str a string to be written.
* @exception IOException if an I/O error occurs.
*/
public final void writeUTF(String str) throws IOException { }
}