public final class FileDescriptor
extends Object 

Since:

JDK1.0

See Also:

FileInputStream, FileOutputStream

• Field Summary

  Fields

  Modifier and Type	Field	Description
  static FileDescriptor	err	A handle to the standard error stream.
  static FileDescriptor	in	A handle to the standard input stream.
  static FileDescriptor	out	A handle to the standard output stream.

• Constructor Summary

  Constructors

  Constructor	Description
  FileDescriptor ()	Constructs an (invalid) FileDescriptor object.

• Method Summary

  All Methods

  Modifier and Type	Method	Description
  void	sync ()	Force all system buffers to synchronize with the underlying device.
  boolean	valid ()	Tests if this file descriptor object is valid.

  • Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

• Field Detail

  • in

    public static final 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:

    System.in

  • out

    public static final 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:

    System.out

  • err

    public static final 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:

    System.err

• Constructor Detail

  • FileDescriptor

    public FileDescriptor()

    Constructs an (invalid) FileDescriptor object.

• Method Detail

  • valid

    public boolean valid()

    Tests if this file descriptor object is valid.

    Returns:

    true if the file descriptor object represents a valid, open file, socket, or other active I/O connection; false otherwise.

  • sync

    public void sync()
     throws SyncFailedException 

    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.

    Since:

    JDK1.1