Skip to content

Most visited

Recently visited

navigation

FileDescriptor

public final class FileDescriptor
extends Object

java.lang.Object
   ↳ java.io.FileDescriptor


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.

See also:

Summary

Fields

public static final FileDescriptor err

A handle to the standard error stream.

public static final FileDescriptor in

A handle to the standard input stream.

public static final FileDescriptor out

A handle to the standard output stream.

Public constructors

FileDescriptor()

Constructs an (invalid) FileDescriptor object.

Public methods

void sync()

Force all system buffers to synchronize with the underlying device.

boolean valid()

Tests if this file descriptor object is valid.

Inherited methods

From class java.lang.Object

Fields

err

Added in API level 1
FileDescriptor err

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 also:

in

Added in API level 1
FileDescriptor in

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 also:

out

Added in API level 1
FileDescriptor out

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 also:

Public constructors

FileDescriptor

Added in API level 1
FileDescriptor ()

Constructs an (invalid) FileDescriptor object.

Public methods

sync

Added in API level 1
void sync ()

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 FileDescriptor 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.

Throws
SyncFailedException Thrown when the buffers cannot be flushed, or because the system cannot guarantee that all the buffers have been synchronized with physical media.

valid

Added in API level 1
boolean valid ()

Tests if this file descriptor object is valid.

Returns
boolean true if the file descriptor object represents a valid, open file, socket, or other active I/O connection; false otherwise.
This site uses cookies to store your preferences for site-specific language and display options.

Hooray!

This class requires API level or higher

This doc is hidden because your selected API level for the documentation is . You can change the documentation API level with the selector above the left navigation.

For more information about specifying the API level your app requires, read Supporting Different Platform Versions.