ChannelGroupFuture.java — netty Source File

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/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package io.netty.channel.group;

import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.util.concurrent.Future;
import io.netty.util.concurrent.GenericFutureListener;

import java.util.Iterator;

/**
 * The result of an asynchronous {@link ChannelGroup} operation.
 * {@link ChannelGroupFuture} is composed of {@link ChannelFuture}s which
 * represent the outcome of the individual I/O operations that affect the
 * {@link Channel}s in the {@link ChannelGroup}.
 *
 * <p>
 * All I/O operations in {@link ChannelGroup} are asynchronous.  It means any
 * I/O calls will return immediately with no guarantee that the requested I/O
 * operations have been completed at the end of the call.  Instead, you will be
 * returned with a {@link ChannelGroupFuture} instance which tells you when the
 * requested I/O operations have succeeded, failed, or cancelled.
 * <p>
 * Various methods are provided to let you check if the I/O operations has been
 * completed, wait for the completion, and retrieve the result of the I/O
 * operation. It also allows you to add more than one
 * {@link ChannelGroupFutureListener} so you can get notified when the I/O
 * operation have been completed.
 *
 * <h3>Prefer {@link #addListener(GenericFutureListener)} to {@link #await()}</h3>
 *
 * It is recommended to prefer {@link #addListener(GenericFutureListener)} to
 * {@link #await()} wherever possible to get notified when I/O operations are
 * done and to do any follow-up tasks.
 * <p>
 * {@link #addListener(GenericFutureListener)} is non-blocking.  It simply
 * adds the specified {@link ChannelGroupFutureListener} to the
 * {@link ChannelGroupFuture}, and I/O thread will notify the listeners when
 * the I/O operations associated with the future is done.
 * {@link ChannelGroupFutureListener} yields the best performance and resource
 * utilization because it does not block at all, but it could be tricky to
 * implement a sequential logic if you are not used to event-driven programming.
 * <p>
 * By contrast, {@link #await()} is a blocking operation.  Once called, the
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