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:
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
| |
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:
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:
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:
FileDescriptor ()
Constructs an (invalid) FileDescriptor object.
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. |
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.
|
Developers