java.io.FileDescriptor Maven / Gradle / Ivy
/*
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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
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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 the file descriptor class serve as an opaque handle
* to the underlying machine-specific structure representing an open
* file, an open socket, or another source or sink of bytes. The
* main practical use for a file descriptor is to create a
* FileInputStream or FileOutputStream to
* contain it.
*
* Applications should not create their own file descriptors.
*
* @author Pavani Diwanji
* @version 1.18, 02/02/00
* @see java.io.FileInputStream
* @see java.io.FileOutputStream
* @since JDK1.0
*/
public final class FileDescriptor
{
/**
* A handle to the standard input stream. Usually, this file
* descriptor is not used directly, but rather via the input stream
* known as System.in.
*
* @see java.lang.System#in
*/
public static final FileDescriptor in = null;
/**
* A handle to the standard output stream. Usually, this file
* descriptor is not used directly, but rather via the output stream
* known as System.out.
* @see java.lang.System#out
*/
public static final FileDescriptor out = null;
/**
* A handle to the standard error stream. Usually, this file
* descriptor is not used directly, but rather via the output stream
* known as System.err.
*
* @see java.lang.System#err
*/
public static final FileDescriptor err = null;
/**
* Constructs an (invalid) FileDescriptor
* object.
*/
public FileDescriptor() { }
/**
* Tests if this file descriptor object is valid.
*
* @return true if the file descriptor object represents a
* valid, open file, socket, or other active I/O connection;
* false otherwise.
*/
public boolean valid() {
return false;
}
/**
* Force all system buffers to synchronize with the underlying
* device. This method returns after all modified data and
* attributes of this FileDescriptor have been written to the
* relevant device(s). In particular, if this FileDescriptor
* refers to a physical storage medium, such as a file in a file
* system, sync will not return until all in-memory modified copies
* of buffers associated with this FileDesecriptor have been
* written to the physical medium.
*
* sync is meant to be used by code that requires physical
* storage (such as a file) to be in a known state For
* example, a class that provided a simple transaction facility
* might use sync to ensure that all changes to a file caused
* by a given transaction were recorded on a storage medium.
*
* sync only affects buffers downstream of this FileDescriptor. If
* any in-memory buffering is being done by the application (for
* example, by a BufferedOutputStream object), those buffers must
* be flushed into the FileDescriptor (for example, by invoking
* OutputStream.flush) before that data will be affected by sync.
*
* @exception SyncFailedException
* Thrown when the buffers cannot be flushed,
* or because the system cannot guarantee that all the
* buffers have been synchronized with physical media.
* @since JDK1.1
*/
public void sync() throws SyncFailedException { }
}