247 lines
9.5 KiB
Java
247 lines
9.5 KiB
Java
/*
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* Copyright (c) 2007, 2013, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.nio.channels.spi;
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import java.nio.channels.*;
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import java.io.IOException;
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import java.util.Iterator;
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import java.util.ServiceLoader;
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import java.util.ServiceConfigurationError;
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import java.util.concurrent.*;
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import java.security.AccessController;
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import java.security.PrivilegedAction;
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/**
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* Service-provider class for asynchronous channels.
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*
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* <p> An asynchronous channel provider is a concrete subclass of this class that
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* has a zero-argument constructor and implements the abstract methods specified
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* below. A given invocation of the Java virtual machine maintains a single
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* system-wide default provider instance, which is returned by the {@link
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* #provider() provider} method. The first invocation of that method will locate
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* the default provider as specified below.
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*
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* <p> All of the methods in this class are safe for use by multiple concurrent
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* threads. </p>
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*
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* @since 1.7
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*/
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public abstract class AsynchronousChannelProvider {
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private static Void checkPermission() {
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SecurityManager sm = System.getSecurityManager();
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if (sm != null)
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sm.checkPermission(new RuntimePermission("asynchronousChannelProvider"));
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return null;
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}
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private AsynchronousChannelProvider(Void ignore) { }
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/**
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* Initializes a new instance of this class.
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*
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* @throws SecurityException
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* If a security manager has been installed and it denies
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* {@link RuntimePermission}{@code ("asynchronousChannelProvider")}
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*/
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protected AsynchronousChannelProvider() {
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this(checkPermission());
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}
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// lazy initialization of default provider
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private static class ProviderHolder {
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static final AsynchronousChannelProvider provider = load();
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private static AsynchronousChannelProvider load() {
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return AccessController
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.doPrivileged(new PrivilegedAction<>() {
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public AsynchronousChannelProvider run() {
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AsynchronousChannelProvider p;
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p = loadProviderFromProperty();
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if (p != null)
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return p;
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p = loadProviderAsService();
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if (p != null)
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return p;
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return sun.nio.ch.DefaultAsynchronousChannelProvider.create();
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}});
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}
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private static AsynchronousChannelProvider loadProviderFromProperty() {
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String cn = System.getProperty("java.nio.channels.spi.AsynchronousChannelProvider");
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if (cn == null)
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return null;
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try {
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@SuppressWarnings("deprecation")
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Object tmp = Class.forName(cn, true,
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ClassLoader.getSystemClassLoader()).newInstance();
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return (AsynchronousChannelProvider)tmp;
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} catch (ClassNotFoundException x) {
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throw new ServiceConfigurationError(null, x);
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} catch (IllegalAccessException x) {
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throw new ServiceConfigurationError(null, x);
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} catch (InstantiationException x) {
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throw new ServiceConfigurationError(null, x);
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} catch (SecurityException x) {
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throw new ServiceConfigurationError(null, x);
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}
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}
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private static AsynchronousChannelProvider loadProviderAsService() {
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ServiceLoader<AsynchronousChannelProvider> sl =
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ServiceLoader.load(AsynchronousChannelProvider.class,
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ClassLoader.getSystemClassLoader());
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Iterator<AsynchronousChannelProvider> i = sl.iterator();
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for (;;) {
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try {
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return (i.hasNext()) ? i.next() : null;
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} catch (ServiceConfigurationError sce) {
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if (sce.getCause() instanceof SecurityException) {
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// Ignore the security exception, try the next provider
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continue;
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}
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throw sce;
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}
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}
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}
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}
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/**
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* Returns the system-wide default asynchronous channel provider for this
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* invocation of the Java virtual machine.
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*
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* <p> The first invocation of this method locates the default provider
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* object as follows: </p>
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*
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* <ol>
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*
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* <li><p> If the system property
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* {@code java.nio.channels.spi.AsynchronousChannelProvider} is defined
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* then it is taken to be the fully-qualified name of a concrete provider class.
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* The class is loaded and instantiated; if this process fails then an
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* unspecified error is thrown. </p></li>
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*
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* <li><p> If a provider class has been installed in a jar file that is
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* visible to the system class loader, and that jar file contains a
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* provider-configuration file named
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* {@code java.nio.channels.spi.AsynchronousChannelProvider} in the resource
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* directory {@code META-INF/services}, then the first class name
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* specified in that file is taken. The class is loaded and
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* instantiated; if this process fails then an unspecified error is
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* thrown. </p></li>
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*
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* <li><p> Finally, if no provider has been specified by any of the above
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* means then the system-default provider class is instantiated and the
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* result is returned. </p></li>
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*
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* </ol>
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*
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* <p> Subsequent invocations of this method return the provider that was
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* returned by the first invocation. </p>
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*
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* @return The system-wide default AsynchronousChannel provider
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*/
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public static AsynchronousChannelProvider provider() {
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return ProviderHolder.provider;
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}
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/**
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* Constructs a new asynchronous channel group with a fixed thread pool.
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*
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* @param nThreads
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* The number of threads in the pool
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* @param threadFactory
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* The factory to use when creating new threads
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*
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* @return A new asynchronous channel group
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*
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* @throws IllegalArgumentException
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* If {@code nThreads <= 0}
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* @throws IOException
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* If an I/O error occurs
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*
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* @see AsynchronousChannelGroup#withFixedThreadPool
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*/
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public abstract AsynchronousChannelGroup
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openAsynchronousChannelGroup(int nThreads, ThreadFactory threadFactory) throws IOException;
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/**
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* Constructs a new asynchronous channel group with the given thread pool.
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*
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* @param executor
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* The thread pool
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* @param initialSize
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* A value {@code >=0} or a negative value for implementation
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* specific default
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*
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* @return A new asynchronous channel group
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*
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* @throws IOException
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* If an I/O error occurs
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*
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* @see AsynchronousChannelGroup#withCachedThreadPool
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*/
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public abstract AsynchronousChannelGroup
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openAsynchronousChannelGroup(ExecutorService executor, int initialSize) throws IOException;
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/**
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* Opens an asynchronous server-socket channel.
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*
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* @param group
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* The group to which the channel is bound, or {@code null} to
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* bind to the default group
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*
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* @return The new channel
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*
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* @throws IllegalChannelGroupException
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* If the provider that created the group differs from this provider
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* @throws ShutdownChannelGroupException
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* The group is shutdown
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* @throws IOException
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* If an I/O error occurs
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*/
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public abstract AsynchronousServerSocketChannel openAsynchronousServerSocketChannel
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(AsynchronousChannelGroup group) throws IOException;
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/**
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* Opens an asynchronous socket channel.
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*
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* @param group
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* The group to which the channel is bound, or {@code null} to
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* bind to the default group
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*
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* @return The new channel
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*
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* @throws IllegalChannelGroupException
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* If the provider that created the group differs from this provider
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* @throws ShutdownChannelGroupException
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* The group is shutdown
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* @throws IOException
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* If an I/O error occurs
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*/
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public abstract AsynchronousSocketChannel openAsynchronousSocketChannel
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(AsynchronousChannelGroup group) throws IOException;
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}
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