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JavaTM 2 Platform Std. Ed. v1.3.1 |
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java.io
Class FileDescriptor
java.lang.Object | +--java.io.FileDescriptor
- public final class FileDescriptor
- extends Object
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.
- Since:
- JDK1.0
- See Also:
FileInputStream,FileOutputStream
| Field Summary | |
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 | |
FileDescriptor()
Constructs an (invalid) FileDescriptor object. |
|
| Method Summary | |
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:
trueif the file descriptor object represents a valid, open file, socket, or other active I/O connection;falseotherwise.
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 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.
- 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
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JavaTM 2 Platform Std. Ed. v1.3.1 |
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For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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