A FileDescriptor
is an opaque representation of a connection to an actual file
in a file system, or to a network socket, or to another source or sink of bytes. The
main practical use for a file descriptor is to create a FileInputStream
(§22.4.3)
or FileOutputStream
(§22.16.3) to contain it.
public final classFileDescriptor
{ public static final FileDescriptorin
= ...; public static final FileDescriptorout
= ...; public static final FileDescriptorerr
= ...; public booleanvalid
(); }
22.26.1 public static final FileDescriptor in = ...
A file descriptor for the standard input stream. Usually, this file descriptor is not
used directly, but rather the input stream known as System.in
(§20.18.1).
22.26.2 public static final FileDescriptor out = ...
A file descriptor for the standard output stream. Usually, this file descriptor is not
used directly, but rather the output stream known as System.out
(§20.18.2).
22.26.3 public static final FileDescriptor err = ...
A file descriptor for the standard error output stream. Usually, this file descriptor
is not used directly, but rather the output stream known as System.err
(§20.18.3).
22.26.4 public boolean valid()
If this FileDescriptor
is valid (represents an active connection to a file or other
active I/O connection), then the result is true
. Otherwise, the result is false
.