Java tutorial
/* * Copyright (c) 2007, 2018, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * 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 * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * 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). * * 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, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.nio.channels; import java.nio.file.*; import java.nio.file.attribute.FileAttribute; import java.nio.file.spi.*; import java.nio.ByteBuffer; import java.io.IOException; import java.util.concurrent.Future; import java.util.concurrent.ExecutorService; import java.util.Set; import java.util.HashSet; import java.util.Collections; /** * An asynchronous channel for reading, writing, and manipulating a file. * * <p> An asynchronous file channel is created when a file is opened by invoking * one of the {@link #open open} methods defined by this class. The file contains * a variable-length sequence of bytes that can be read and written and whose * current size can be {@link #size() 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 truncated}. * * <p> An asynchronous file channel does not have a <i>current position</i> * within the file. Instead, the file position is specified to each read and * write method that initiates asynchronous operations. A {@link CompletionHandler} * is specified as a parameter and is invoked to consume the result of the I/O * operation. This class also defines read and write methods that initiate * asynchronous operations, returning a {@link Future} to represent the pending * result of the operation. The {@code Future} may be used to check if the * operation has completed, wait for its completion, and retrieve the result. * * <p> In addition to read and write operations, this class defines the * following operations: </p> * * <ul> * * <li><p> Updates made to a file may be {@link #force <i>forced * out</i>} to the underlying storage device, ensuring that data are not * lost in the event of a system crash. </p></li> * * <li><p> A region of a file may be {@link #lock <i>locked</i>} against * access by other programs. </p></li> * * </ul> * * <p> An {@code AsynchronousFileChannel} is associated with a thread pool to * which tasks are submitted to handle I/O events and dispatch to completion * handlers that consume the results of I/O operations on the channel. The * completion handler for an I/O operation initiated on a channel is guaranteed * to be invoked by one of the threads in the thread pool (This ensures that the * completion handler is run by a thread with the expected <em>identity</em>). * Where an I/O operation completes immediately, and the initiating thread is * itself a thread in the thread pool, then the completion handler may be invoked * directly by the initiating thread. When an {@code AsynchronousFileChannel} is * created without specifying a thread pool then the channel is associated with * a system-dependent default thread pool that may be shared with other * channels. The default thread pool is configured by the system properties * defined by the {@link AsynchronousChannelGroup} class. * * <p> Channels of this type 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. This causes all outstanding asynchronous * operations on the channel to complete with the exception {@link * AsynchronousCloseException}. Multiple read and write operations may be * outstanding at the same time. When multiple read and write operations are * outstanding then the ordering of the I/O operations, and the order that the * completion handlers are invoked, is not specified; they are not, in particular, * guaranteed to execute in the order that the operations were initiated. The * {@link java.nio.ByteBuffer ByteBuffers} used when reading or writing are not * safe for use by multiple concurrent I/O operations. Furthermore, after an I/O * operation is initiated then care should be taken to ensure that the buffer is * not accessed until after the operation has completed. * * <p> As with {@link FileChannel}, 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. * * @since 1.7 */ public abstract class AsynchronousFileChannel implements AsynchronousChannel { /** * Initializes a new instance of this class. */ protected AsynchronousFileChannel() { } /** * Opens or creates a file for reading and/or writing, returning an * asynchronous file channel to access the file. * * <p> The {@code options} parameter determines how the file is opened. * The {@link StandardOpenOption#READ READ} and {@link StandardOpenOption#WRITE * WRITE} options determines if the file should be opened for reading and/or * writing. If neither option is contained in the array then an existing file * is opened for reading. * * <p> In addition to {@code READ} and {@code WRITE}, the following options * may be present: * * <table class="striped"> * <caption style="display:none">additional options</caption> * <thead> * <tr> <th scope="col">Option</th> <th scope="col">Description</th> </tr> * </thead> * <tbody> * <tr> * <th scope="row"> {@link StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING} </th> * <td> When opening an existing file, the file is first truncated to a * size of 0 bytes. This option is ignored when the file is opened only * for reading.</td> * </tr> * <tr> * <th scope="row"> {@link StandardOpenOption#CREATE_NEW CREATE_NEW} </th> * <td> If this option is present then a new file is created, failing if * the file already exists. When creating a file the check for the * existence of the file and the creation of the file if it does not exist * is atomic with respect to other file system operations. This option is * ignored when the file is opened only for reading. </td> * </tr> * <tr> * <th scope="row" > {@link StandardOpenOption#CREATE CREATE} </th> * <td> If this option is present then an existing file is opened if it * exists, otherwise a new file is created. When creating a file the check * for the existence of the file and the creation of the file if it does * not exist is atomic with respect to other file system operations. This * option is ignored if the {@code CREATE_NEW} option is also present or * the file is opened only for reading. </td> * </tr> * <tr> * <th scope="row" > {@link StandardOpenOption#DELETE_ON_CLOSE DELETE_ON_CLOSE} </th> * <td> When this option is present then the implementation makes a * <em>best effort</em> attempt to delete the file when closed by * the {@link #close close} method. If the {@code close} method is not * invoked then a <em>best effort</em> attempt is made to delete the file * when the Java virtual machine terminates. </td> * </tr> * <tr> * <th scope="row">{@link StandardOpenOption#SPARSE SPARSE} </th> * <td> When creating a new file this option is a <em>hint</em> that the * new file will be sparse. This option is ignored when not creating * a new file. </td> * </tr> * <tr> * <th scope="row"> {@link StandardOpenOption#SYNC SYNC} </th> * <td> Requires that every update to the file's content or metadata be * written synchronously to the underlying storage device. (see <a * href="../file/package-summary.html#integrity"> Synchronized I/O file * integrity</a>). </td> * </tr> * <tr> * <th scope="row"> {@link StandardOpenOption#DSYNC DSYNC} </th> * <td> Requires that every update to the file's content be written * synchronously to the underlying storage device. (see <a * href="../file/package-summary.html#integrity"> Synchronized I/O file * integrity</a>). </td> * </tr> * </tbody> * </table> * * <p> An implementation may also support additional options. * * <p> The {@code executor} parameter is the {@link ExecutorService} to * which tasks are submitted to handle I/O events and dispatch completion * results for operations initiated on resulting channel. * The nature of these tasks is highly implementation specific and so care * should be taken when configuring the {@code Executor}. Minimally it * should support an unbounded work queue and should not run tasks on the * caller thread of the {@link ExecutorService#execute execute} method. * Shutting down the executor service while the channel is open results in * unspecified behavior. * * <p> The {@code attrs} parameter is an optional array of file {@link * FileAttribute file-attributes} to set atomically when creating the file. * * <p> The new channel is created by invoking the {@link * FileSystemProvider#newFileChannel newFileChannel} method on the * provider that created the {@code Path}. * * @param file * The path of the file to open or create * @param options * Options specifying how the file is opened * @param executor * The thread pool or {@code null} to associate the channel with * the default thread pool * @param attrs * An optional list of file attributes to set atomically when * creating the file * * @return A new asynchronous file channel * * @throws IllegalArgumentException * If the set contains an invalid combination of options * @throws UnsupportedOperationException * If the {@code file} is associated with a provider that does not * support creating asynchronous file channels, or an unsupported * open option is specified, or the array contains an attribute that * cannot be set atomically when creating the file * @throws IOException * If an I/O error occurs * @throws SecurityException * If a security manager is installed and it denies an * unspecified permission required by the implementation. * In the case of the default provider, the {@link * SecurityManager#checkRead(String)} method is invoked to check * read access if the file is opened for reading. The {@link * SecurityManager#checkWrite(String)} method is invoked to check * write access if the file is opened for writing */ public static AsynchronousFileChannel open(Path file, Set<? extends OpenOption> options, ExecutorService executor, FileAttribute<?>... attrs) throws IOException { FileSystemProvider provider = file.getFileSystem().provider(); return provider.newAsynchronousFileChannel(file, options, executor, attrs); } @SuppressWarnings({ "unchecked", "rawtypes" }) // generic array construction private static final FileAttribute<?>[] NO_ATTRIBUTES = new FileAttribute[0]; /** * Opens or creates a file for reading and/or writing, returning an * asynchronous file channel to access the file. * * <p> An invocation of this method behaves in exactly the same way as the * invocation * <pre> * ch.{@link #open(Path,Set,ExecutorService,FileAttribute[]) * open}(file, opts, null, new FileAttribute<?>[0]); * </pre> * where {@code opts} is a {@code Set} containing the options specified to * this method. * * <p> The resulting channel is associated with default thread pool to which * tasks are submitted to handle I/O events and dispatch to completion * handlers that consume the result of asynchronous operations performed on * the resulting channel. * * @param file * The path of the file to open or create * @param options * Options specifying how the file is opened * * @return A new asynchronous file channel * * @throws IllegalArgumentException * If the set contains an invalid combination of options * @throws UnsupportedOperationException * If the {@code file} is associated with a provider that does not * support creating file channels, or an unsupported open option is * specified * @throws IOException * If an I/O error occurs * @throws SecurityException * If a security manager is installed and it denies an * unspecified permission required by the implementation. * In the case of the default provider, the {@link * SecurityManager#checkRead(String)} method is invoked to check * read access if the file is opened for reading. The {@link * SecurityManager#checkWrite(String)} method is invoked to check * write access if the file is opened for writing */ public static AsynchronousFileChannel open(Path file, OpenOption... options) throws IOException { Set<OpenOption> set; if (options.length == 0) { set = Collections.emptySet(); } else { set = new HashSet<>(); Collections.addAll(set, options); } return open(file, set, null, NO_ATTRIBUTES); } /** * Returns the current size of this channel's file. * * @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. * * <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. </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 AsynchronousFileChannel truncate(long size) throws IOException; /** * 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 {@code metaData} parameter can be used to limit the number of * I/O operations that this method is required to perform. Passing * {@code false} for this parameter indicates that only updates to the * file's content need be written to storage; passing {@code 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. * * <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. * * @param metaData * If {@code 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 ClosedChannelException * If this channel is closed * * @throws IOException * If some other I/O error occurs */ public abstract void force(boolean metaData) throws IOException; /** * Acquires a lock on the given region of this channel's file. * * <p> This method initiates an operation to acquire a lock on the given * region of this channel's file. The {@code handler} parameter is a * completion handler that is invoked when the lock is acquired (or the * operation fails). The result passed to the completion handler is the * resulting {@code FileLock}. * * <p> The region specified by the {@code position} and {@code 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 two-argument * {@link #lock(Object,CompletionHandler)} method simply locks a region * of size {@link Long#MAX_VALUE}. If a lock that overlaps the requested * region is already held by this Java virtual machine, or this method has * been invoked to lock an overlapping region and that operation has not * completed, then this method throws {@link OverlappingFileLockException}. * * <p> Some operating systems do not support a mechanism to acquire a file * lock in an asynchronous manner. Consequently an implementation may * acquire the file lock in a background thread or from a task executed by * a thread in the associated thread pool. If there are many lock operations * outstanding then it may consume threads in the Java virtual machine for * indefinite periods. * * <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. * * @param <A> * The type of the attachment * @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 * {@code position} + {@code size} must be non-negative * @param shared * {@code true} to request a shared lock, in which case this * channel must be open for reading (and possibly writing); * {@code false} to request an exclusive lock, in which case this * channel must be open for writing (and possibly reading) * @param attachment * The object to attach to the I/O operation; can be {@code null} * @param handler * The handler for consuming the result * * @throws OverlappingFileLockException * If a lock that overlaps the requested region is already held by * this Java virtual machine, or there is already a pending attempt * to lock an overlapping region * @throws IllegalArgumentException * If the preconditions on the parameters do not hold * @throws NonReadableChannelException * If {@code shared} is true but this channel was not opened for reading * @throws NonWritableChannelException * If {@code shared} is false but this channel was not opened for writing */ public abstract <A> void lock(long position, long size, boolean shared, A attachment, CompletionHandler<FileLock, ? super A> handler); /** * Acquires an exclusive lock on this channel's file. * * <p> This method initiates an operation to acquire a lock on the given * region of this channel's file. The {@code handler} parameter is a * completion handler that is invoked when the lock is acquired (or the * operation fails). The result passed to the completion handler is the * resulting {@code FileLock}. * * <p> An invocation of this method of the form {@code ch.lock(att,handler)} * behaves in exactly the same way as the invocation * <pre> * ch.{@link #lock(long,long,boolean,Object,CompletionHandler) lock}(0L, Long.MAX_VALUE, false, att, handler) * </pre> * * @param <A> * The type of the attachment * @param attachment * The object to attach to the I/O operation; can be {@code null} * @param handler * The handler for consuming the result * * @throws OverlappingFileLockException * If a lock is already held by this Java virtual machine, or there * is already a pending attempt to lock a region * @throws NonWritableChannelException * If this channel was not opened for writing */ public final <A> void lock(A attachment, CompletionHandler<FileLock, ? super A> handler) { lock(0L, Long.MAX_VALUE, false, attachment, handler); } /** * Acquires a lock on the given region of this channel's file. * * <p> This method initiates an operation to acquire a lock on the given * region of this channel's file. The method behaves in exactly the same * manner as the {@link #lock(long, long, boolean, Object, CompletionHandler)} * method except that instead of specifying a completion handler, this * method returns a {@code Future} representing the pending result. The * {@code Future}'s {@link Future#get() get} method returns the {@link * FileLock} on successful completion. * * @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 * {@code position} + {@code size} must be non-negative * @param shared * {@code true} to request a shared lock, in which case this * channel must be open for reading (and possibly writing); * {@code false} to request an exclusive lock, in which case this * channel must be open for writing (and possibly reading) * * @return a {@code Future} object representing the pending result * * @throws OverlappingFileLockException * If a lock is already held by this Java virtual machine, or there * is already a pending attempt to lock a region * @throws IllegalArgumentException * If the preconditions on the parameters do not hold * @throws NonReadableChannelException * If {@code shared} is true but this channel was not opened for reading * @throws NonWritableChannelException * If {@code shared} is false but this channel was not opened for writing */ public abstract Future<FileLock> lock(long position, long size, boolean shared); /** * Acquires an exclusive lock on this channel's file. * * <p> This method initiates an operation to acquire an exclusive lock on this * channel's file. The method returns a {@code Future} representing the * pending result of the operation. The {@code Future}'s {@link Future#get() * get} method returns the {@link FileLock} on successful completion. * * <p> An invocation of this method behaves in exactly the same way as the * invocation * <pre> * ch.{@link #lock(long,long,boolean) lock}(0L, Long.MAX_VALUE, false) * </pre> * * @return a {@code Future} object representing the pending result * * @throws OverlappingFileLockException * If a lock is already held by this Java virtual machine, or there * is already a pending attempt to lock a region * @throws NonWritableChannelException * If this channel was not opened for writing */ public final Future<FileLock> lock() { return lock(0L, Long.MAX_VALUE, false); } /** * 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 {@code null}. If it fails to acquire * a lock for any other reason then an appropriate exception is thrown. * * @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 * {@code position} + {@code size} must be non-negative * * @param shared * {@code true} to request a shared lock, * {@code false} to request an exclusive lock * * @return A lock object representing the newly-acquired lock, * or {@code null} 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 NonReadableChannelException * If {@code shared} is true but this channel was not opened for reading * @throws NonWritableChannelException * If {@code shared} is false but this channel was not opened for writing * * @throws IOException * If some other I/O error occurs * * @see #lock(Object,CompletionHandler) * @see #lock(long,long,boolean,Object,CompletionHandler) * @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. * * <p> An invocation of this method of the form {@code ch.tryLock()} * behaves in exactly the same way as the invocation * * <pre> * ch.{@link #tryLock(long,long,boolean) tryLock}(0L, Long.MAX_VALUE, false) </pre> * * @return A lock object representing the newly-acquired lock, * or {@code null} 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 NonWritableChannelException * If {@code shared} is false but this channel was not opened for writing * * @throws IOException * If some other I/O error occurs * * @see #lock(Object,CompletionHandler) * @see #lock(long,long,boolean,Object,CompletionHandler) * @see #tryLock(long,long,boolean) */ public final FileLock tryLock() throws IOException { return tryLock(0L, Long.MAX_VALUE, false); } /** * Reads a sequence of bytes from this channel into the given buffer, * starting at the given file position. * * <p> This method initiates the reading of a sequence of bytes from this * channel into the given buffer, starting at the given file position. The * result of the read is the number of bytes read or {@code -1} if the given * position is greater than or equal to the file's size at the time that the * read is attempted. * * <p> This method works in the same manner as the {@link * AsynchronousByteChannel#read(ByteBuffer,Object,CompletionHandler)} * method, except that bytes are read starting at the given file position. * If the given file position is greater than the file's size at the time * that the read is attempted then no bytes are read. * * @param <A> * The type of the attachment * @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 * @param attachment * The object to attach to the I/O operation; can be {@code null} * @param handler * The handler for consuming the result * * @throws IllegalArgumentException * If the position is negative or the buffer is read-only * @throws NonReadableChannelException * If this channel was not opened for reading */ public abstract <A> void read(ByteBuffer dst, long position, A attachment, CompletionHandler<Integer, ? super A> handler); /** * Reads a sequence of bytes from this channel into the given buffer, * starting at the given file position. * * <p> This method initiates the reading of a sequence of bytes from this * channel into the given buffer, starting at the given file position. This * method returns a {@code Future} representing the pending result of the * operation. The {@code Future}'s {@link Future#get() get} method returns * the number of bytes read or {@code -1} if the given position is greater * than or equal to the file's size at the time that the read is attempted. * * <p> This method works in the same manner as the {@link * AsynchronousByteChannel#read(ByteBuffer)} method, except that bytes are * read starting at the given file position. If the given file position is * greater than the file's size at the time that the read is attempted then * no bytes are read. * * @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 A {@code Future} object representing the pending result * * @throws IllegalArgumentException * If the position is negative or the buffer is read-only * @throws NonReadableChannelException * If this channel was not opened for reading */ public abstract Future<Integer> read(ByteBuffer dst, long position); /** * 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 * AsynchronousByteChannel#write(ByteBuffer,Object,CompletionHandler)} * method, except that bytes are written starting at the given file position. * If the given position is greater than the file's size, at the time that * the write is attempted, 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. * * @param <A> * The type of the attachment * @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 * @param attachment * The object to attach to the I/O operation; can be {@code null} * @param handler * The handler for consuming the result * * @throws IllegalArgumentException * If the position is negative * @throws NonWritableChannelException * If this channel was not opened for writing */ public abstract <A> void write(ByteBuffer src, long position, A attachment, CompletionHandler<Integer, ? super A> handler); /** * Writes a sequence of bytes to this channel from the given buffer, starting * at the given file position. * * <p> This method initiates the writing of a sequence of bytes to this * channel from the given buffer, starting at the given file position. The * method returns a {@code Future} representing the pending result of the * write operation. The {@code Future}'s {@link Future#get() get} method * returns the number of bytes written. * * <p> This method works in the same manner as the {@link * AsynchronousByteChannel#write(ByteBuffer)} method, except that bytes are * written starting at the given file position. If the given position is * greater than the file's size, at the time that the write is attempted, * 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. * * @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 A {@code Future} object representing the pending result * * @throws IllegalArgumentException * If the position is negative * @throws NonWritableChannelException * If this channel was not opened for writing */ public abstract Future<Integer> write(ByteBuffer src, long position); }