https://openjdk.java.net/ 
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 * Copyright (c) 2000, 2005, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
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 * particular file as subject to the "Classpath" exception as provided
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 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
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 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
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 *
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package java.nio.channels;

import java.io.*;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.spi.AbstractInterruptibleChannel;



A channel for reading, writing, mapping, and manipulating a file.

 A file channel has a current position within its file which can be both queried and modified. The file itself contains a variable-length sequence of bytes that can be read and written and whose current size can be queried. The size of the file increases when bytes are written beyond its current size; the size of the file decreases when it is truncated. The file may also have some associated metadata such as access
permissions, content type, and last-modification time; this class does not
define methods for metadata access.

 In addition to the familiar read, write, and close operations of byte
channels, this class defines the following file-specific operations: 


    
  
  •  Bytes may be read or written at an absolute position in a file in a way that does not affect the channel's current position. 
    • 
  
  •  A region of a file may be mapped directly into memory; for large files this is often much more efficient than invoking the usual read or write methods.
  
    • 
  
  •  Updates made to a file may be forced
  out to the underlying storage device, ensuring that data are not lost in the event of a system crash. 
    • 
  
  •  Bytes can be transferred from a file to
  some other channel, and vice
  versa, in a way that can be optimized by many operating systems into a very fast transfer directly to or from the filesystem cache. 
    • 
  
  •  A region of a file may be locked against access by other programs. 
    • 



 File channels are safe for use by multiple concurrent threads. The close method may be invoked at any time, as specified by the Channel interface. Only one operation that involves the channel's position or can change its file's size may be in progress at any given time; attempts to initiate a second such operation while the first is still in progress will block until the first operation completes. Other operations, in particular those that take an explicit position, may proceed concurrently; whether they in fact do so is dependent upon the underlying implementation and is therefore unspecified. 
 The view of a file provided by an instance of this class is guaranteed
to be consistent with other views of the same file provided by other
instances in the same program.  The view provided by an instance of this
class may or may not, however, be consistent with the views seen by other
concurrently-running programs due to caching performed by the underlying
operating system and delays induced by network-filesystem protocols.  This
is true regardless of the language in which these other programs are
written, and whether they are running on the same machine or on some other
machine.  The exact nature of any such inconsistencies are system-dependent
and are therefore unspecified.

 This class does not define methods for opening existing files or for creating new ones; such methods may be added in a future release. In this release a file channel can be obtained from an existing FileInputStream, FileOutputStream, or RandomAccessFile object by invoking that object's getChannel method, which returns a file channel that
is connected to the same underlying file.

 The state of a file channel is intimately connected to that of the
object whose getChannel method returned the channel.  Changing the
channel's position, whether explicitly or by reading or writing bytes, will
change the file position of the originating object, and vice versa.
Changing the file's length via the file channel will change the length seen
via the originating object, and vice versa.  Changing the file's content by
writing bytes will change the content seen by the originating object, and
vice versa.

 At various points this class specifies that an instance that is "open for reading," "open for writing," or "open for reading and writing" is required. A channel obtained via the getChannel method of a FileInputStream instance will be open for reading. A channel obtained via the getChannel method of a FileOutputStream instance will be open for writing. Finally, a channel obtained via the getChannel method of a RandomAccessFile instance will be open for reading if the instance was created with mode "r" and will be open for reading and writing
if the instance was created with mode "rw".

 A file channel that is open for writing may be in
append mode, for example if it was obtained from a file-output stream that was created by invoking the 
FileOutputStream(File,boolean) constructor and passing true for
the second parameter.  In this mode each invocation of a relative write
operation first advances the position to the end of the file and then writes
the requested data.  Whether the advancement of the position and the writing
of the data are done in a single atomic operation is system-dependent and
therefore unspecified.

Author:Mark Reinhold, Mike McCloskey, JSR-51 Expert Group
See Also:
Since:1.4
/**
 * A channel for reading, writing, mapping, and manipulating a file.
 *
 * <p> A file channel has a current <i>position</i> within its file which can
 * be both {@link #position() </code>queried<code>} and {@link #position(long)
 * </code>modified<code>}.  The file itself contains a variable-length sequence
 * of bytes that can be read and written and whose current {@link #size
 * </code><i>size</i><code>} can be queried.  The size of the file increases
 * when bytes are written beyond its current size; the size of the file
 * decreases when it is {@link #truncate </code><i>truncated</i><code>}.  The
 * file may also have some associated <i>metadata</i> such as access
 * permissions, content type, and last-modification time; this class does not
 * define methods for metadata access.
 *
 * <p> In addition to the familiar read, write, and close operations of byte
 * channels, this class defines the following file-specific operations: </p>
 *
 * <ul>
 *
 *   <li><p> Bytes may be {@link #read(ByteBuffer, long) </code>read<code>} or
 *   {@link #write(ByteBuffer, long) </code>written<code>} at an absolute
 *   position in a file in a way that does not affect the channel's current
 *   position.  </p></li>
 *
 *   <li><p> A region of a file may be {@link #map </code>mapped<code>}
 *   directly into memory; for large files this is often much more efficient
 *   than invoking the usual <tt>read</tt> or <tt>write</tt> methods.
 *   </p></li>
 *
 *   <li><p> Updates made to a file may be {@link #force </code>forced
 *   out<code>} to the underlying storage device, ensuring that data are not
 *   lost in the event of a system crash.  </p></li>
 *
 *   <li><p> Bytes can be transferred from a file {@link #transferTo </code>to
 *   some other channel<code>}, and {@link #transferFrom </code>vice
 *   versa<code>}, in a way that can be optimized by many operating systems
 *   into a very fast transfer directly to or from the filesystem cache.
 *   </p></li>
 *
 *   <li><p> A region of a file may be {@link FileLock </code>locked<code>}
 *   against access by other programs.  </p></li>
 *
 * </ul>
 *
 * <p> File channels are safe for use by multiple concurrent threads.  The
 * {@link Channel#close close} method may be invoked at any time, as specified
 * by the {@link Channel} interface.  Only one operation that involves the
 * channel's position or can change its file's size may be in progress at any
 * given time; attempts to initiate a second such operation while the first is
 * still in progress will block until the first operation completes.  Other
 * operations, in particular those that take an explicit position, may proceed
 * concurrently; whether they in fact do so is dependent upon the underlying
 * implementation and is therefore unspecified.
 *
 * <p> The view of a file provided by an instance of this class is guaranteed
 * to be consistent with other views of the same file provided by other
 * instances in the same program.  The view provided by an instance of this
 * class may or may not, however, be consistent with the views seen by other
 * concurrently-running programs due to caching performed by the underlying
 * operating system and delays induced by network-filesystem protocols.  This
 * is true regardless of the language in which these other programs are
 * written, and whether they are running on the same machine or on some other
 * machine.  The exact nature of any such inconsistencies are system-dependent
 * and are therefore unspecified.
 *
 * <p> This class does not define methods for opening existing files or for
 * creating new ones; such methods may be added in a future release.  In this
 * release a file channel can be obtained from an existing {@link
 * java.io.FileInputStream#getChannel FileInputStream}, {@link
 * java.io.FileOutputStream#getChannel FileOutputStream}, or {@link
 * java.io.RandomAccessFile#getChannel RandomAccessFile} object by invoking
 * that object's <tt>getChannel</tt> method, which returns a file channel that
 * is connected to the same underlying file.
 *
 * <p> The state of a file channel is intimately connected to that of the
 * object whose <tt>getChannel</tt> method returned the channel.  Changing the
 * channel's position, whether explicitly or by reading or writing bytes, will
 * change the file position of the originating object, and vice versa.
 * Changing the file's length via the file channel will change the length seen
 * via the originating object, and vice versa.  Changing the file's content by
 * writing bytes will change the content seen by the originating object, and
 * vice versa.
 *
 * <a name="open-mode"><p> At various points this class specifies that an
 * instance that is "open for reading," "open for writing," or "open for
 * reading and writing" is required.  A channel obtained via the {@link
 * java.io.FileInputStream#getChannel getChannel} method of a {@link
 * java.io.FileInputStream} instance will be open for reading.  A channel
 * obtained via the {@link java.io.FileOutputStream#getChannel getChannel}
 * method of a {@link java.io.FileOutputStream} instance will be open for
 * writing.  Finally, a channel obtained via the {@link
 * java.io.RandomAccessFile#getChannel getChannel} method of a {@link
 * java.io.RandomAccessFile} instance will be open for reading if the instance
 * was created with mode <tt>"r"</tt> and will be open for reading and writing
 * if the instance was created with mode <tt>"rw"</tt>.
 *
 * <a name="append-mode"><p> A file channel that is open for writing may be in
 * <i>append mode</i>, for example if it was obtained from a file-output stream
 * that was created by invoking the {@link
 * java.io.FileOutputStream#FileOutputStream(java.io.File,boolean)
 * FileOutputStream(File,boolean)} constructor and passing <tt>true</tt> for
 * the second parameter.  In this mode each invocation of a relative write
 * operation first advances the position to the end of the file and then writes
 * the requested data.  Whether the advancement of the position and the writing
 * of the data are done in a single atomic operation is system-dependent and
 * therefore unspecified.
 *
 *
 * @see java.io.FileInputStream#getChannel()
 * @see java.io.FileOutputStream#getChannel()
 * @see java.io.RandomAccessFile#getChannel()
 *
 * @author Mark Reinhold
 * @author Mike McCloskey
 * @author JSR-51 Expert Group
 * @since 1.4
 */

public abstract class FileChannel
    extends AbstractInterruptibleChannel
    implements ByteChannel, GatheringByteChannel, ScatteringByteChannel
{

    
Initializes a new instance of this class.

/**
     * Initializes a new instance of this class.
     */
    protected FileChannel() { }


    // -- Channel operations --

    
Reads a sequence of bytes from this channel into the given buffer.

 Bytes are read starting at this channel's current file position, and then the file position is updated with the number of bytes actually read. Otherwise this method behaves exactly as specified in the ReadableByteChannel interface. 


/**
     * Reads a sequence of bytes from this channel into the given buffer.
     *
     * <p> Bytes are read starting at this channel's current file position, and
     * then the file position is updated with the number of bytes actually
     * read.  Otherwise this method behaves exactly as specified in the {@link
     * ReadableByteChannel} interface. </p>
     */
    public abstract int read(ByteBuffer dst) throws IOException;

    
Reads a sequence of bytes from this channel into a subsequence of the
given buffers.

 Bytes are read starting at this channel's current file position, and then the file position is updated with the number of bytes actually read. Otherwise this method behaves exactly as specified in the ScatteringByteChannel interface. 


/**
     * Reads a sequence of bytes from this channel into a subsequence of the
     * given buffers.
     *
     * <p> Bytes are read starting at this channel's current file position, and
     * then the file position is updated with the number of bytes actually
     * read.  Otherwise this method behaves exactly as specified in the {@link
     * ScatteringByteChannel} interface.  </p>
     */
    public abstract long read(ByteBuffer[] dsts, int offset, int length)
        throws IOException;

    
Reads a sequence of bytes from this channel into the given buffers.

 Bytes are read starting at this channel's current file position, and then the file position is updated with the number of bytes actually read. Otherwise this method behaves exactly as specified in the ScatteringByteChannel interface. 


/**
     * Reads a sequence of bytes from this channel into the given buffers.
     *
     * <p> Bytes are read starting at this channel's current file position, and
     * then the file position is updated with the number of bytes actually
     * read.  Otherwise this method behaves exactly as specified in the {@link
     * ScatteringByteChannel} interface.  </p>
     */
    public final long read(ByteBuffer[] dsts) throws IOException {
        return read(dsts, 0, dsts.length);
    }

    
Writes a sequence of bytes to this channel from the given buffer.

 Bytes are written starting at this channel's current file position unless the channel is in append mode, in which case the position is first advanced to the end of the file. The file is grown, if necessary, to accommodate the written bytes, and then the file position is updated with the number of bytes actually written. Otherwise this method behaves exactly as specified by the WritableByteChannel interface. 


/**
     * Writes a sequence of bytes to this channel from the given buffer.
     *
     * <p> Bytes are written starting at this channel's current file position
     * unless the channel is in append mode, in which case the position is
     * first advanced to the end of the file.  The file is grown, if necessary,
     * to accommodate the written bytes, and then the file position is updated
     * with the number of bytes actually written.  Otherwise this method
     * behaves exactly as specified by the {@link WritableByteChannel}
     * interface. </p>
     */
    public abstract int write(ByteBuffer src) throws IOException;

    
Writes a sequence of bytes to this channel from a subsequence of the
given buffers.

 Bytes are written starting at this channel's current file position unless the channel is in append mode, in which case the position is first advanced to the end of the file. The file is grown, if necessary, to accommodate the written bytes, and then the file position is updated with the number of bytes actually written. Otherwise this method behaves exactly as specified in the GatheringByteChannel interface. 


/**
     * Writes a sequence of bytes to this channel from a subsequence of the
     * given buffers.
     *
     * <p> Bytes are written starting at this channel's current file position
     * unless the channel is in append mode, in which case the position is
     * first advanced to the end of the file.  The file is grown, if necessary,
     * to accommodate the written bytes, and then the file position is updated
     * with the number of bytes actually written.  Otherwise this method
     * behaves exactly as specified in the {@link GatheringByteChannel}
     * interface.  </p>
     */
    public abstract long write(ByteBuffer[] srcs, int offset, int length)
        throws IOException;

    
Writes a sequence of bytes to this channel from the given buffers.

 Bytes are written starting at this channel's current file position unless the channel is in append mode, in which case the position is first advanced to the end of the file. The file is grown, if necessary, to accommodate the written bytes, and then the file position is updated with the number of bytes actually written. Otherwise this method behaves exactly as specified in the GatheringByteChannel interface. 


/**
     * Writes a sequence of bytes to this channel from the given buffers.
     *
     * <p> Bytes are written starting at this channel's current file position
     * unless the channel is in append mode, in which case the position is
     * first advanced to the end of the file.  The file is grown, if necessary,
     * to accommodate the written bytes, and then the file position is updated
     * with the number of bytes actually written.  Otherwise this method
     * behaves exactly as specified in the {@link GatheringByteChannel}
     * interface.  </p>
     */
    public final long write(ByteBuffer[] srcs) throws IOException {
        return write(srcs, 0, srcs.length);
    }


    // -- Other operations --

    
Returns this channel's file position.  


Throws:
Returns: This channel's file position,
         a non-negative integer counting the number of bytes
         from the beginning of the file to the current position
/**
     * Returns this channel's file position.  </p>
     *
     * @return  This channel's file position,
     *          a non-negative integer counting the number of bytes
     *          from the beginning of the file to the current position
     *
     * @throws  ClosedChannelException
     *          If this channel is closed
     *
     * @throws  IOException
     *          If some other I/O error occurs
     */
    public abstract long position() throws IOException;

    
Sets this channel's file position.

 Setting the position to a value that is greater than the file's
current size is legal but does not change the size of the file.  A later
attempt to read bytes at such a position will immediately return an
end-of-file indication.  A later attempt to write bytes at such a
position will cause the file to be grown to accommodate the new bytes;
the values of any bytes between the previous end-of-file and the
newly-written bytes are unspecified.  


Params:
  • newPosition – 
        The new position, a non-negative integer counting
        the number of bytes from the beginning of the file
Throws:
Returns: This file channel
/**
     * Sets this channel's file position.
     *
     * <p> Setting the position to a value that is greater than the file's
     * current size is legal but does not change the size of the file.  A later
     * attempt to read bytes at such a position will immediately return an
     * end-of-file indication.  A later attempt to write bytes at such a
     * position will cause the file to be grown to accommodate the new bytes;
     * the values of any bytes between the previous end-of-file and the
     * newly-written bytes are unspecified.  </p>
     *
     * @param  newPosition
     *         The new position, a non-negative integer counting
     *         the number of bytes from the beginning of the file
     *
     * @return  This file channel
     *
     * @throws  ClosedChannelException
     *          If this channel is closed
     *
     * @throws  IllegalArgumentException
     *          If the new position is negative
     *
     * @throws  IOException
     *          If some other I/O error occurs
     */
    public abstract FileChannel position(long newPosition) throws IOException;

    
Returns the current size of this channel's file. 


Throws:
Returns: The current size of this channel's file,
         measured in bytes
/**
     * Returns the current size of this channel's file. </p>
     *
     * @return  The current size of this channel's file,
     *          measured in bytes
     *
     * @throws  ClosedChannelException
     *          If this channel is closed
     *
     * @throws  IOException
     *          If some other I/O error occurs
     */
    public abstract long size() throws IOException;

    
Truncates this channel's file to the given size.

 If the given size is less than the file's current size then the file
is truncated, discarding any bytes beyond the new end of the file.  If
the given size is greater than or equal to the file's current size then
the file is not modified.  In either case, if this channel's file
position is greater than the given size then it is set to that size.



Params:
  • size – 
        The new size, a non-negative byte count
Throws:
Returns: This file channel
/**
     * Truncates this channel's file to the given size.
     *
     * <p> If the given size is less than the file's current size then the file
     * is truncated, discarding any bytes beyond the new end of the file.  If
     * the given size is greater than or equal to the file's current size then
     * the file is not modified.  In either case, if this channel's file
     * position is greater than the given size then it is set to that size.
     * </p>
     *
     * @param  size
     *         The new size, a non-negative byte count
     *
     * @return  This file channel
     *
     * @throws  NonWritableChannelException
     *          If this channel was not opened for writing
     *
     * @throws  ClosedChannelException
     *          If this channel is closed
     *
     * @throws  IllegalArgumentException
     *          If the new size is negative
     *
     * @throws  IOException
     *          If some other I/O error occurs
     */
    public abstract FileChannel truncate(long size) throws IOException;

    
Forces any updates to this channel's file to be written to the storage
device that contains it.

 If this channel's file resides on a local storage device then when
this method returns it is guaranteed that all changes made to the file
since this channel was created, or since this method was last invoked,
will have been written to that device.  This is useful for ensuring that
critical information is not lost in the event of a system crash.

 If the file does not reside on a local device then no such guarantee
is made.

 The metaData parameter can be used to limit the number of
I/O operations that this method is required to perform.  Passing
false for this parameter indicates that only updates to the
file's content need be written to storage; passing true
indicates that updates to both the file's content and metadata must be
written, which generally requires at least one more I/O operation.
Whether this parameter actually has any effect is dependent upon the
underlying operating system and is therefore unspecified.

 Invoking this method may cause an I/O operation to occur even if the
channel was only opened for reading.  Some operating systems, for
example, maintain a last-access time as part of a file's metadata, and
this time is updated whenever the file is read.  Whether or not this is
actually done is system-dependent and is therefore unspecified.

 This method is only guaranteed to force changes that were made to this channel's file via the methods defined in this class. It may or may not force changes that were made by modifying the content of a mapped byte buffer obtained by invoking the map method. Invoking the force method of the mapped byte buffer will force changes made to the buffer's content to be written. 


Params:
  • metaData – 
         If true then this method is required to force changes
         to both the file's content and metadata to be written to
         storage; otherwise, it need only force content changes to be
         written
Throws:
/**
     * Forces any updates to this channel's file to be written to the storage
     * device that contains it.
     *
     * <p> If this channel's file resides on a local storage device then when
     * this method returns it is guaranteed that all changes made to the file
     * since this channel was created, or since this method was last invoked,
     * will have been written to that device.  This is useful for ensuring that
     * critical information is not lost in the event of a system crash.
     *
     * <p> If the file does not reside on a local device then no such guarantee
     * is made.
     *
     * <p> The <tt>metaData</tt> parameter can be used to limit the number of
     * I/O operations that this method is required to perform.  Passing
     * <tt>false</tt> for this parameter indicates that only updates to the
     * file's content need be written to storage; passing <tt>true</tt>
     * indicates that updates to both the file's content and metadata must be
     * written, which generally requires at least one more I/O operation.
     * Whether this parameter actually has any effect is dependent upon the
     * underlying operating system and is therefore unspecified.
     *
     * <p> Invoking this method may cause an I/O operation to occur even if the
     * channel was only opened for reading.  Some operating systems, for
     * example, maintain a last-access time as part of a file's metadata, and
     * this time is updated whenever the file is read.  Whether or not this is
     * actually done is system-dependent and is therefore unspecified.
     *
     * <p> This method is only guaranteed to force changes that were made to
     * this channel's file via the methods defined in this class.  It may or
     * may not force changes that were made by modifying the content of a
     * {@link MappedByteBuffer </code>mapped byte buffer<code>} obtained by
     * invoking the {@link #map map} method.  Invoking the {@link
     * MappedByteBuffer#force force} method of the mapped byte buffer will
     * force changes made to the buffer's content to be written.  </p>
     *
     * @param   metaData
     *          If <tt>true</tt> then this method is required to force changes
     *          to both the file's content and metadata to be written to
     *          storage; otherwise, it need only force content changes to be
     *          written
     *
     * @throws  ClosedChannelException
     *          If this channel is closed
     *
     * @throws  IOException
     *          If some other I/O error occurs
     */
    public abstract void force(boolean metaData) throws IOException;

    
Transfers bytes from this channel's file to the given writable byte
channel.

 An attempt is made to read up to count bytes starting at
the given position in this channel's file and write them to the
target channel.  An invocation of this method may or may not transfer
all of the requested bytes; whether or not it does so depends upon the
natures and states of the channels.  Fewer than the requested number of
bytes are transferred if this channel's file contains fewer than
count bytes starting at the given position, or if the
target channel is non-blocking and it has fewer than count
bytes free in its output buffer.

 This method does not modify this channel's position.  If the given
position is greater than the file's current size then no bytes are
transferred.  If the target channel has a position then bytes are
written starting at that position and then the position is incremented
by the number of bytes written.

 This method is potentially much more efficient than a simple loop
that reads from this channel and writes to the target channel.  Many
operating systems can transfer bytes directly from the filesystem cache
to the target channel without actually copying them.  


Params:
  • position – 
        The position within the file at which the transfer is to begin;
        must be non-negative
  • count – 
        The maximum number of bytes to be transferred; must be
        non-negative
  • target – 
        The target channel
Throws:
Returns: The number of bytes, possibly zero,
         that were actually transferred
/**
     * Transfers bytes from this channel's file to the given writable byte
     * channel.
     *
     * <p> An attempt is made to read up to <tt>count</tt> bytes starting at
     * the given <tt>position</tt> in this channel's file and write them to the
     * target channel.  An invocation of this method may or may not transfer
     * all of the requested bytes; whether or not it does so depends upon the
     * natures and states of the channels.  Fewer than the requested number of
     * bytes are transferred if this channel's file contains fewer than
     * <tt>count</tt> bytes starting at the given <tt>position</tt>, or if the
     * target channel is non-blocking and it has fewer than <tt>count</tt>
     * bytes free in its output buffer.
     *
     * <p> This method does not modify this channel's position.  If the given
     * position is greater than the file's current size then no bytes are
     * transferred.  If the target channel has a position then bytes are
     * written starting at that position and then the position is incremented
     * by the number of bytes written.
     *
     * <p> This method is potentially much more efficient than a simple loop
     * that reads from this channel and writes to the target channel.  Many
     * operating systems can transfer bytes directly from the filesystem cache
     * to the target channel without actually copying them.  </p>
     *
     * @param  position
     *         The position within the file at which the transfer is to begin;
     *         must be non-negative
     *
     * @param  count
     *         The maximum number of bytes to be transferred; must be
     *         non-negative
     *
     * @param  target
     *         The target channel
     *
     * @return  The number of bytes, possibly zero,
     *          that were actually transferred
     *
     * @throws IllegalArgumentException
     *         If the preconditions on the parameters do not hold
     *
     * @throws  NonReadableChannelException
     *          If this channel was not opened for reading
     *
     * @throws  NonWritableChannelException
     *          If the target channel was not opened for writing
     *
     * @throws  ClosedChannelException
     *          If either this channel or the target channel is closed
     *
     * @throws  AsynchronousCloseException
     *          If another thread closes either channel
     *          while the transfer is in progress
     *
     * @throws  ClosedByInterruptException
     *          If another thread interrupts the current thread while the
     *          transfer is in progress, thereby closing both channels and
     *          setting the current thread's interrupt status
     *
     * @throws  IOException
     *          If some other I/O error occurs
     */
    public abstract long transferTo(long position, long count,
                                    WritableByteChannel target)
        throws IOException;

    
Transfers bytes into this channel's file from the given readable byte
channel.

 An attempt is made to read up to count bytes from the
source channel and write them to this channel's file starting at the
given position.  An invocation of this method may or may not
transfer all of the requested bytes; whether or not it does so depends
upon the natures and states of the channels.  Fewer than the requested
number of bytes will be transferred if the source channel has fewer than
count bytes remaining, or if the source channel is non-blocking
and has fewer than count bytes immediately available in its
input buffer.

 This method does not modify this channel's position.  If the given
position is greater than the file's current size then no bytes are
transferred.  If the source channel has a position then bytes are read
starting at that position and then the position is incremented by the
number of bytes read.

 This method is potentially much more efficient than a simple loop
that reads from the source channel and writes to this channel.  Many
operating systems can transfer bytes directly from the source channel
into the filesystem cache without actually copying them.  


Params:
  • src – 
        The source channel
  • position – 
        The position within the file at which the transfer is to begin;
        must be non-negative
  • count – 
        The maximum number of bytes to be transferred; must be
        non-negative
Throws:
Returns: The number of bytes, possibly zero,
         that were actually transferred
/**
     * Transfers bytes into this channel's file from the given readable byte
     * channel.
     *
     * <p> An attempt is made to read up to <tt>count</tt> bytes from the
     * source channel and write them to this channel's file starting at the
     * given <tt>position</tt>.  An invocation of this method may or may not
     * transfer all of the requested bytes; whether or not it does so depends
     * upon the natures and states of the channels.  Fewer than the requested
     * number of bytes will be transferred if the source channel has fewer than
     * <tt>count</tt> bytes remaining, or if the source channel is non-blocking
     * and has fewer than <tt>count</tt> bytes immediately available in its
     * input buffer.
     *
     * <p> This method does not modify this channel's position.  If the given
     * position is greater than the file's current size then no bytes are
     * transferred.  If the source channel has a position then bytes are read
     * starting at that position and then the position is incremented by the
     * number of bytes read.
     *
     * <p> This method is potentially much more efficient than a simple loop
     * that reads from the source channel and writes to this channel.  Many
     * operating systems can transfer bytes directly from the source channel
     * into the filesystem cache without actually copying them.  </p>
     *
     * @param  src
     *         The source channel
     *
     * @param  position
     *         The position within the file at which the transfer is to begin;
     *         must be non-negative
     *
     * @param  count
     *         The maximum number of bytes to be transferred; must be
     *         non-negative
     *
     * @return  The number of bytes, possibly zero,
     *          that were actually transferred
     *
     * @throws IllegalArgumentException
     *         If the preconditions on the parameters do not hold
     *
     * @throws  NonReadableChannelException
     *          If the source channel was not opened for reading
     *
     * @throws  NonWritableChannelException
     *          If this channel was not opened for writing
     *
     * @throws  ClosedChannelException
     *          If either this channel or the source channel is closed
     *
     * @throws  AsynchronousCloseException
     *          If another thread closes either channel
     *          while the transfer is in progress
     *
     * @throws  ClosedByInterruptException
     *          If another thread interrupts the current thread while the
     *          transfer is in progress, thereby closing both channels and
     *          setting the current thread's interrupt status
     *
     * @throws  IOException
     *          If some other I/O error occurs
     */
    public abstract long transferFrom(ReadableByteChannel src,
                                      long position, long count)
        throws IOException;

    
Reads a sequence of bytes from this channel into the given buffer,
starting at the given file position.

 This method works in the same manner as the read(ByteBuffer) method, except that bytes are read starting at the given file position rather than at the channel's current position. This method does not modify this channel's position. If the given position is greater than the file's current size then no bytes are read. 


Params:
  • dst – 
        The buffer into which bytes are to be transferred
  • position – 
        The file position at which the transfer is to begin;
        must be non-negative
Throws:
Returns: The number of bytes read, possibly zero, or -1 if the
         given position is greater than or equal to the file's current
         size
/**
     * Reads a sequence of bytes from this channel into the given buffer,
     * starting at the given file position.
     *
     * <p> This method works in the same manner as the {@link
     * #read(ByteBuffer)} method, except that bytes are read starting at the
     * given file position rather than at the channel's current position.  This
     * method does not modify this channel's position.  If the given position
     * is greater than the file's current size then no bytes are read.  </p>
     *
     * @param  dst
     *         The buffer into which bytes are to be transferred
     *
     * @param  position
     *         The file position at which the transfer is to begin;
     *         must be non-negative
     *
     * @return  The number of bytes read, possibly zero, or <tt>-1</tt> if the
     *          given position is greater than or equal to the file's current
     *          size
     *
     * @throws  IllegalArgumentException
     *          If the position is negative
     *
     * @throws  NonReadableChannelException
     *          If this channel was not opened for reading
     *
     * @throws  ClosedChannelException
     *          If this channel is closed
     *
     * @throws  AsynchronousCloseException
     *          If another thread closes this channel
     *          while the read operation is in progress
     *
     * @throws  ClosedByInterruptException
     *          If another thread interrupts the current thread
     *          while the read operation is in progress, thereby
     *          closing the channel and setting the current thread's
     *          interrupt status
     *
     * @throws  IOException
     *          If some other I/O error occurs
     */
    public abstract int read(ByteBuffer dst, long position) throws IOException;

    
Writes a sequence of bytes to this channel from the given buffer,
starting at the given file position.

 This method works in the same manner as the write(ByteBuffer) method, except that bytes are written starting at the given file position rather than at the channel's current position. This method does not modify this channel's position. If the given position is greater than the file's current size then the file will be grown to accommodate the new bytes; the values of any bytes between the previous end-of-file and the newly-written bytes are unspecified. 


Params:
  • src – 
        The buffer from which bytes are to be transferred
  • position – 
        The file position at which the transfer is to begin;
        must be non-negative
Throws:
Returns: The number of bytes written, possibly zero
/**
     * Writes a sequence of bytes to this channel from the given buffer,
     * starting at the given file position.
     *
     * <p> This method works in the same manner as the {@link
     * #write(ByteBuffer)} method, except that bytes are written starting at
     * the given file position rather than at the channel's current position.
     * This method does not modify this channel's position.  If the given
     * position is greater than the file's current size then the file will be
     * grown to accommodate the new bytes; the values of any bytes between the
     * previous end-of-file and the newly-written bytes are unspecified.  </p>
     *
     * @param  src
     *         The buffer from which bytes are to be transferred
     *
     * @param  position
     *         The file position at which the transfer is to begin;
     *         must be non-negative
     *
     * @return  The number of bytes written, possibly zero
     *
     * @throws  IllegalArgumentException
     *          If the position is negative
     *
     * @throws  NonWritableChannelException
     *          If this channel was not opened for writing
     *
     * @throws  ClosedChannelException
     *          If this channel is closed
     *
     * @throws  AsynchronousCloseException
     *          If another thread closes this channel
     *          while the write operation is in progress
     *
     * @throws  ClosedByInterruptException
     *          If another thread interrupts the current thread
     *          while the write operation is in progress, thereby
     *          closing the channel and setting the current thread's
     *          interrupt status
     *
     * @throws  IOException
     *          If some other I/O error occurs
     */
    public abstract int write(ByteBuffer src, long position) throws IOException;


    // -- Memory-mapped buffers --

    
A typesafe enumeration for file-mapping modes.

See Also:
Since:1.4
/**
     * A typesafe enumeration for file-mapping modes.
     *
     * @since 1.4
     *
     * @see java.nio.channels.FileChannel#map
     */
    public static class MapMode {

        
Mode for a read-only mapping.

/**
         * Mode for a read-only mapping.
         */
        public static final MapMode READ_ONLY
            = new MapMode("READ_ONLY");

        
Mode for a read/write mapping.

/**
         * Mode for a read/write mapping.
         */
        public static final MapMode READ_WRITE
            = new MapMode("READ_WRITE");

        
Mode for a private (copy-on-write) mapping.

/**
         * Mode for a private (copy-on-write) mapping.
         */
        public static final MapMode PRIVATE
            = new MapMode("PRIVATE");

        private final String name;

        private MapMode(String name) {
            this.name = name;
        }

        
Returns a string describing this file-mapping mode.

Returns: A descriptive string
/**
         * Returns a string describing this file-mapping mode.
         *
         * @return  A descriptive string
         */
        public String toString() {
            return name;
        }

    }

    
Maps a region of this channel's file directly into memory.

 A region of a file may be mapped into memory in one of three modes:



    
  
  •  Read-only: Any attempt to modify the resulting buffer will cause a ReadOnlyBufferException to be thrown. (MapMode.READ_ONLY) 
    • 
  
  •  Read/write: Changes made to the resulting buffer will eventually be propagated to the file; they may or may not be made visible to other programs that have mapped the same file. (MapMode.READ_WRITE) 
    • 
  
  •  Private: Changes made to the resulting buffer will not be propagated to the file and will not be visible to other programs that have mapped the same file; instead, they will cause private copies of the modified portions of the buffer to be created. (MapMode.PRIVATE) 
    • 



 For a read-only mapping, this channel must have been opened for
reading; for a read/write or private mapping, this channel must have
been opened for both reading and writing.

 The mapped byte buffer returned by this method will have a position of zero and a limit and capacity of size; its mark will be undefined.  The buffer and
the mapping that it represents will remain valid until the buffer itself
is garbage-collected.

 A mapping, once established, is not dependent upon the file channel
that was used to create it.  Closing the channel, in particular, has no
effect upon the validity of the mapping.

 Many of the details of memory-mapped files are inherently dependent
upon the underlying operating system and are therefore unspecified.  The
behavior of this method when the requested region is not completely
contained within this channel's file is unspecified.  Whether changes
made to the content or size of the underlying file, by this program or
another, are propagated to the buffer is unspecified.  The rate at which
changes to the buffer are propagated to the file is unspecified.

 For most operating systems, mapping a file into memory is more expensive than reading or writing a few tens of kilobytes of data via the usual read and write methods. From the standpoint of performance it is generally only worth mapping relatively large files into memory. 


Params:
  • mode –  One of the constants READ_ONLY, READ_WRITE, or 
        PRIVATE defined in the MapMode class, according to whether the file is to be mapped read-only, read/write, or privately (copy-on-write), respectively
  • position – 
        The position within the file at which the mapped region
        is to start; must be non-negative
  • size –  The size of the region to be mapped; must be non-negative and no greater than Integer.MAX_VALUE
Throws:
See Also:
/**
     * Maps a region of this channel's file directly into memory.
     *
     * <p> A region of a file may be mapped into memory in one of three modes:
     * </p>
     *
     * <ul type=disc>
     *
     *   <li><p> <i>Read-only:</i> Any attempt to modify the resulting buffer
     *   will cause a {@link java.nio.ReadOnlyBufferException} to be thrown.
     *   ({@link MapMode#READ_ONLY MapMode.READ_ONLY}) </p></li>
     *
     *   <li><p> <i>Read/write:</i> Changes made to the resulting buffer will
     *   eventually be propagated to the file; they may or may not be made
     *   visible to other programs that have mapped the same file.  ({@link
     *   MapMode#READ_WRITE MapMode.READ_WRITE}) </p></li>
     *
     *   <li><p> <i>Private:</i> Changes made to the resulting buffer will not
     *   be propagated to the file and will not be visible to other programs
     *   that have mapped the same file; instead, they will cause private
     *   copies of the modified portions of the buffer to be created.  ({@link
     *   MapMode#PRIVATE MapMode.PRIVATE}) </p></li>
     *
     * </ul>
     *
     * <p> For a read-only mapping, this channel must have been opened for
     * reading; for a read/write or private mapping, this channel must have
     * been opened for both reading and writing.
     *
     * <p> The {@link MappedByteBuffer </code>mapped byte buffer<code>}
     * returned by this method will have a position of zero and a limit and
     * capacity of <tt>size</tt>; its mark will be undefined.  The buffer and
     * the mapping that it represents will remain valid until the buffer itself
     * is garbage-collected.
     *
     * <p> A mapping, once established, is not dependent upon the file channel
     * that was used to create it.  Closing the channel, in particular, has no
     * effect upon the validity of the mapping.
     *
     * <p> Many of the details of memory-mapped files are inherently dependent
     * upon the underlying operating system and are therefore unspecified.  The
     * behavior of this method when the requested region is not completely
     * contained within this channel's file is unspecified.  Whether changes
     * made to the content or size of the underlying file, by this program or
     * another, are propagated to the buffer is unspecified.  The rate at which
     * changes to the buffer are propagated to the file is unspecified.
     *
     * <p> For most operating systems, mapping a file into memory is more
     * expensive than reading or writing a few tens of kilobytes of data via
     * the usual {@link #read read} and {@link #write write} methods.  From the
     * standpoint of performance it is generally only worth mapping relatively
     * large files into memory.  </p>
     *
     * @param  mode
     *         One of the constants {@link MapMode#READ_ONLY READ_ONLY}, {@link
     *         MapMode#READ_WRITE READ_WRITE}, or {@link MapMode#PRIVATE
     *         PRIVATE} defined in the {@link MapMode} class, according to
     *         whether the file is to be mapped read-only, read/write, or
     *         privately (copy-on-write), respectively
     *
     * @param  position
     *         The position within the file at which the mapped region
     *         is to start; must be non-negative
     *
     * @param  size
     *         The size of the region to be mapped; must be non-negative and
     *         no greater than {@link java.lang.Integer#MAX_VALUE}
     *
     * @throws NonReadableChannelException
     *         If the <tt>mode</tt> is {@link MapMode#READ_ONLY READ_ONLY} but
     *         this channel was not opened for reading
     *
     * @throws NonWritableChannelException
     *         If the <tt>mode</tt> is {@link MapMode#READ_WRITE READ_WRITE} or
     *         {@link MapMode#PRIVATE PRIVATE} but this channel was not opened
     *         for both reading and writing
     *
     * @throws IllegalArgumentException
     *         If the preconditions on the parameters do not hold
     *
     * @throws IOException
     *         If some other I/O error occurs
     *
     * @see java.nio.channels.FileChannel.MapMode
     * @see java.nio.MappedByteBuffer
     */
    public abstract MappedByteBuffer map(MapMode mode,
                                         long position, long size)
        throws IOException;


    // -- Locks --

    
Acquires a lock on the given region of this channel's file.

 An invocation of this method will block until the region can be
locked, this channel is closed, or the invoking thread is interrupted,
whichever comes first.

 If this channel is closed by another thread during an invocation of this method then an AsynchronousCloseException will be thrown. 
 If the invoking thread is interrupted while waiting to acquire the lock then its interrupt status will be set and a FileLockInterruptionException will be thrown. If the invoker's interrupt status is set when this method is invoked then that exception will be thrown immediately; the thread's interrupt status will not be changed. 
 The region specified by the position and size parameters need not be contained within, or even overlap, the actual underlying file. Lock regions are fixed in size; if a locked region initially contains the end of the file and the file grows beyond the region then the new portion of the file will not be covered by the lock. If a file is expected to grow in size and a lock on the entire file is required then a region starting at zero, and no smaller than the expected maximum size of the file, should be locked. The zero-argument lock() method simply locks a region of size Long.MAX_VALUE. 
 Some operating systems do not support shared locks, in which case a request for a shared lock is automatically converted into a request for an exclusive lock. Whether the newly-acquired lock is shared or exclusive may be tested by invoking the resulting lock object's isShared method. 
 File locks are held on behalf of the entire Java virtual machine.
They are not suitable for controlling access to a file by multiple
threads within the same virtual machine.  


Params:
  • position – 
        The position at which the locked region is to start; must be
        non-negative
  • size – 
        The size of the locked region; must be non-negative, and the sum
        position + size must be non-negative
  • shared – 
        true to request a shared lock, in which case this
        channel must be open for reading (and possibly writing);
        false to request an exclusive lock, in which case this
        channel must be open for writing (and possibly reading)
Throws:
See Also:
Returns: A lock object representing the newly-acquired lock
/**
     * Acquires a lock on the given region of this channel's file.
     *
     * <p> An invocation of this method will block until the region can be
     * locked, this channel is closed, or the invoking thread is interrupted,
     * whichever comes first.
     *
     * <p> If this channel is closed by another thread during an invocation of
     * this method then an {@link AsynchronousCloseException} will be thrown.
     *
     * <p> If the invoking thread is interrupted while waiting to acquire the
     * lock then its interrupt status will be set and a {@link
     * FileLockInterruptionException} will be thrown.  If the invoker's
     * interrupt status is set when this method is invoked then that exception
     * will be thrown immediately; the thread's interrupt status will not be
     * changed.
     *
     * <p> The region specified by the <tt>position</tt> and <tt>size</tt>
     * parameters need not be contained within, or even overlap, the actual
     * underlying file.  Lock regions are fixed in size; if a locked region
     * initially contains the end of the file and the file grows beyond the
     * region then the new portion of the file will not be covered by the lock.
     * If a file is expected to grow in size and a lock on the entire file is
     * required then a region starting at zero, and no smaller than the
     * expected maximum size of the file, should be locked.  The zero-argument
     * {@link #lock()} method simply locks a region of size {@link
     * Long#MAX_VALUE}.
     *
     * <p> Some operating systems do not support shared locks, in which case a
     * request for a shared lock is automatically converted into a request for
     * an exclusive lock.  Whether the newly-acquired lock is shared or
     * exclusive may be tested by invoking the resulting lock object's {@link
     * FileLock#isShared() isShared} method.
     *
     * <p> File locks are held on behalf of the entire Java virtual machine.
     * They are not suitable for controlling access to a file by multiple
     * threads within the same virtual machine.  </p>
     *
     * @param  position
     *         The position at which the locked region is to start; must be
     *         non-negative
     *
     * @param  size
     *         The size of the locked region; must be non-negative, and the sum
     *         <tt>position</tt>&nbsp;+&nbsp;<tt>size</tt> must be non-negative
     *
     * @param  shared
     *         <tt>true</tt> to request a shared lock, in which case this
     *         channel must be open for reading (and possibly writing);
     *         <tt>false</tt> to request an exclusive lock, in which case this
     *         channel must be open for writing (and possibly reading)
     *
     * @return  A lock object representing the newly-acquired lock
     *
     * @throws  IllegalArgumentException
     *          If the preconditions on the parameters do not hold
     *
     * @throws  ClosedChannelException
     *          If this channel is closed
     *
     * @throws  AsynchronousCloseException
     *          If another thread closes this channel while the invoking
     *          thread is blocked in this method
     *
     * @throws  FileLockInterruptionException
     *          If the invoking thread is interrupted while blocked in this
     *          method
     *
     * @throws  OverlappingFileLockException
     *          If a lock that overlaps the requested region is already held by
     *          this Java virtual machine, or if another thread is already
     *          blocked in this method and is attempting to lock an overlapping
     *          region
     *
     * @throws  NonReadableChannelException
     *          If <tt>shared</tt> is <tt>true</tt> this channel was not
     *          opened for reading
     *
     * @throws  NonWritableChannelException
     *          If <tt>shared</tt> is <tt>false</tt> but this channel was not
     *          opened for writing
     *
     * @throws  IOException
     *          If some other I/O error occurs
     *
     * @see     #lock()
     * @see     #tryLock()
     * @see     #tryLock(long,long,boolean)
     */
    public abstract FileLock lock(long position, long size, boolean shared)
        throws IOException;

    
Acquires an exclusive lock on this channel's file.

 An invocation of this method of the form fc.lock() behaves
in exactly the same way as the invocation

 fc.lock(0L, Long.MAX_VALUE, false) 


Throws:
See Also:
Returns: A lock object representing the newly-acquired lock
/**
     * Acquires an exclusive lock on this channel's file.
     *
     * <p> An invocation of this method of the form <tt>fc.lock()</tt> behaves
     * in exactly the same way as the invocation
     *
     * <pre>
     *     fc.{@link #lock(long,long,boolean) lock}(0L, Long.MAX_VALUE, false) </pre>
     *
     * @return  A lock object representing the newly-acquired lock
     *
     * @throws  ClosedChannelException
     *          If this channel is closed
     *
     * @throws  AsynchronousCloseException
     *          If another thread closes this channel while the invoking
     *          thread is blocked in this method
     *
     * @throws  FileLockInterruptionException
     *          If the invoking thread is interrupted while blocked in this
     *          method
     *
     * @throws  OverlappingFileLockException
     *          If a lock that overlaps the requested region is already held by
     *          this Java virtual machine, or if another thread is already
     *          blocked in this method and is attempting to lock an overlapping
     *          region of the same file
     *
     * @throws  NonWritableChannelException
     *          If this channel was not opened for writing
     *
     * @throws  IOException
     *          If some other I/O error occurs
     *
     * @see     #lock(long,long,boolean)
     * @see     #tryLock()
     * @see     #tryLock(long,long,boolean)
     */
    public final FileLock lock() throws IOException {
        return lock(0L, Long.MAX_VALUE, false);
    }

    
Attempts to acquire a lock on the given region of this channel's file.

 This method does not block.  An invocation always returns
immediately, either having acquired a lock on the requested region or
having failed to do so.  If it fails to acquire a lock because an
overlapping lock is held by another program then it returns
null.  If it fails to acquire a lock for any other reason then
an appropriate exception is thrown.

 The region specified by the position and size parameters need not be contained within, or even overlap, the actual underlying file. Lock regions are fixed in size; if a locked region initially contains the end of the file and the file grows beyond the region then the new portion of the file will not be covered by the lock. If a file is expected to grow in size and a lock on the entire file is required then a region starting at zero, and no smaller than the expected maximum size of the file, should be locked. The zero-argument tryLock() method simply locks a region of size Long.MAX_VALUE. 
 Some operating systems do not support shared locks, in which case a request for a shared lock is automatically converted into a request for an exclusive lock. Whether the newly-acquired lock is shared or exclusive may be tested by invoking the resulting lock object's isShared method. 
 File locks are held on behalf of the entire Java virtual machine.
They are not suitable for controlling access to a file by multiple
threads within the same virtual machine.  


Params:
  • position – 
        The position at which the locked region is to start; must be
        non-negative
  • size – 
        The size of the locked region; must be non-negative, and the sum
        position + size must be non-negative
  • shared – 
        true to request a shared lock,
        false to request an exclusive lock
Throws:
See Also:
Returns: A lock object representing the newly-acquired lock,
         or null if the lock could not be acquired
         because another program holds an overlapping lock
/**
     * Attempts to acquire a lock on the given region of this channel's file.
     *
     * <p> This method does not block.  An invocation always returns
     * immediately, either having acquired a lock on the requested region or
     * having failed to do so.  If it fails to acquire a lock because an
     * overlapping lock is held by another program then it returns
     * <tt>null</tt>.  If it fails to acquire a lock for any other reason then
     * an appropriate exception is thrown.
     *
     * <p> The region specified by the <tt>position</tt> and <tt>size</tt>
     * parameters need not be contained within, or even overlap, the actual
     * underlying file.  Lock regions are fixed in size; if a locked region
     * initially contains the end of the file and the file grows beyond the
     * region then the new portion of the file will not be covered by the lock.
     * If a file is expected to grow in size and a lock on the entire file is
     * required then a region starting at zero, and no smaller than the
     * expected maximum size of the file, should be locked.  The zero-argument
     * {@link #tryLock()} method simply locks a region of size {@link
     * Long#MAX_VALUE}.
     *
     * <p> Some operating systems do not support shared locks, in which case a
     * request for a shared lock is automatically converted into a request for
     * an exclusive lock.  Whether the newly-acquired lock is shared or
     * exclusive may be tested by invoking the resulting lock object's {@link
     * FileLock#isShared() isShared} method.
     *
     * <p> File locks are held on behalf of the entire Java virtual machine.
     * They are not suitable for controlling access to a file by multiple
     * threads within the same virtual machine.  </p>
     *
     * @param  position
     *         The position at which the locked region is to start; must be
     *         non-negative
     *
     * @param  size
     *         The size of the locked region; must be non-negative, and the sum
     *         <tt>position</tt>&nbsp;+&nbsp;<tt>size</tt> must be non-negative
     *
     * @param  shared
     *         <tt>true</tt> to request a shared lock,
     *         <tt>false</tt> to request an exclusive lock
     *
     * @return  A lock object representing the newly-acquired lock,
     *          or <tt>null</tt> if the lock could not be acquired
     *          because another program holds an overlapping lock
     *
     * @throws  IllegalArgumentException
     *          If the preconditions on the parameters do not hold
     *
     * @throws  ClosedChannelException
     *          If this channel is closed
     *
     * @throws  OverlappingFileLockException
     *          If a lock that overlaps the requested region is already held by
     *          this Java virtual machine, or if another thread is already
     *          blocked in this method and is attempting to lock an overlapping
     *          region of the same file
     *
     * @throws  IOException
     *          If some other I/O error occurs
     *
     * @see     #lock()
     * @see     #lock(long,long,boolean)
     * @see     #tryLock()
     */
    public abstract FileLock tryLock(long position, long size, boolean shared)
        throws IOException;

    
Attempts to acquire an exclusive lock on this channel's file.

 An invocation of this method of the form fc.tryLock()
behaves in exactly the same way as the invocation

 fc.tryLock(0L, Long.MAX_VALUE, false) 


Throws:
  • ClosedChannelException – 
         If this channel is closed
  • OverlappingFileLockException – 
         If a lock that overlaps the requested region is already held by
         this Java virtual machine, or if another thread is already
         blocked in this method and is attempting to lock an overlapping
         region
  • IOException – 
         If some other I/O error occurs
See Also:
Returns: A lock object representing the newly-acquired lock,
         or null if the lock could not be acquired
         because another program holds an overlapping lock
/**
     * Attempts to acquire an exclusive lock on this channel's file.
     *
     * <p> An invocation of this method of the form <tt>fc.tryLock()</tt>
     * behaves in exactly the same way as the invocation
     *
     * <pre>
     *     fc.{@link #tryLock(long,long,boolean) tryLock}(0L, Long.MAX_VALUE, false) </pre>
     *
     * @return  A lock object representing the newly-acquired lock,
     *          or <tt>null</tt> if the lock could not be acquired
     *          because another program holds an overlapping lock
     *
     * @throws  ClosedChannelException
     *          If this channel is closed
     *
     * @throws  OverlappingFileLockException
     *          If a lock that overlaps the requested region is already held by
     *          this Java virtual machine, or if another thread is already
     *          blocked in this method and is attempting to lock an overlapping
     *          region
     *
     * @throws  IOException
     *          If some other I/O error occurs
     *
     * @see     #lock()
     * @see     #lock(long,long,boolean)
     * @see     #tryLock(long,long,boolean)
     */
    public final FileLock tryLock() throws IOException {
        return tryLock(0L, Long.MAX_VALUE, false);
    }

}