public abstract class MappedByteBuffer extends ByteBuffer
Mapped byte buffers are created via the FileChannel.map method. This class
extends the ByteBuffer class with operations that are specific to
memory-mapped file regions.
A mapped byte buffer and the file mapping that it represents remain valid until the buffer itself is garbage-collected.
The content of a mapped byte buffer can change at any time, for example
if the content of the corresponding region of the mapped file is changed by
this program or another. Whether or not such changes occur, and when they
occur, is operating-system dependent and therefore unspecified.
All or part of a mapped byte buffer may become
inaccessible at any time, for example if the mapped file is truncated. An
attempt to access an inaccessible region of a mapped byte buffer will not
change the buffer's content and will cause an unspecified exception to be
thrown either at the time of the access or at some later time. It is
therefore strongly recommended that appropriate precautions be taken to
avoid the manipulation of a mapped file by this program, or by a
concurrently running program, except to read or write the file's content.
Mapped byte buffers otherwise behave no differently than ordinary direct
byte buffers.
| Modifier and Type | Method and Description |
|---|---|
MappedByteBuffer |
force ()
Forces any changes made to this buffer's content to be written to the
storage device containing the mapped file.
|
boolean |
isLoaded ()
Tells whether or not this buffer's content is resident in physical
memory.
|
MappedByteBuffer |
load ()
Loads this buffer's content into physical memory.
|
allocate, allocateDirect, array, arrayOffset, asCharBuffer, asDoubleBuffer, asFloatBuffer, asIntBuffer, asLongBuffer, asReadOnlyBuffer, asShortBuffer, compact, compareTo, duplicate, equals, get, get, get, get, getChar, getChar, getDouble, getDouble, getFloat, getFloat, getInt, getInt, getLong, getLong, getShort, getShort, hasArray, hashCode, isDirect, order, order, put, put, put, put, put, putChar, putChar, putDouble, putDouble, putFloat, putFloat, putInt, putInt, putLong, putLong, putShort, putShort, slice, toString, wrap, wrap public final boolean isLoaded()
A return value of true implies that it is highly likely that all of the data in this buffer is resident in physical memory and may therefore be accessed without incurring any virtual-memory page faults or I/O operations. A return value of false does not necessarily imply that the buffer's content is not resident in physical memory.
The returned value is a hint, rather than a guarantee, because the underlying operating system may have paged out some of the buffer's data by the time that an invocation of this method returns.
public final MappedByteBuffer load()
This method makes a best effort to ensure that, when it returns, this buffer's content is resident in physical memory. Invoking this method may cause some number of page faults and I/O operations to occur.
public final MappedByteBuffer force()
If the file mapped into this buffer resides on a local storage device then when this method returns it is guaranteed that all changes made to the buffer since it was created, or since this method was last invoked, will have been written to that device.
If the file does not reside on a local device then no such guarantee is made.
If this buffer was not mapped in read/write mode (FileChannel.MapMode.READ_WRITE) then invoking this
method has no effect.
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For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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