GeezerVison is showing docs.oracle.com — FileDescriptor (Java SE 25 & JDK 25)
Class 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:
- 1.0
-
Field Summary
Fields
Modifier and Type
Field
Description
A handle to the standard error stream.
A handle to the standard input stream.
A handle to the standard output stream.
-
Constructor Summary
Constructors
Constructor
Description
Constructs an (invalid) FileDescriptor object.
-
Method Summary
Modifier and Type
Method
Description
void
Force all system buffers to synchronize with the underlying
device.
boolean
Tests if this file descriptor object is valid.
Methods declared in class Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
-
Field Details
-
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
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:
-
-
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:
-
-
Constructor Details
-
FileDescriptor
public FileDescriptor()
Constructs an (invalid) FileDescriptor object.
The fd or handle is set later.
-
Method Details
-
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
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:
- 1.1
|