每次写Netty代码的时候第一行都会写下面的代码：

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EventLoopGroup boss = new NioEventLoopGroup();
EventLoopGroup worker = new NioEventLoopGroup();

所以源码解析也从EventLoopGroup开始。该篇只是简单列举了几个接口，缺乏实现类所以功能描述上有所欠缺。

解析

EventLoopGroup

EventLoopGroup继承了EventExecutorGroup接口，而EventExecutorGroup接口继承了定时/延时任务ScheduledExecutorService接口，所以EventLoopGroup实现类会实现线程池接口。

EventLoopGroup继承关系

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public interface EventLoopGroup extends EventExecutorGroup {
    @Override
    EventLoop next();
    // 注册channel到EventLoop，注册完成时会通知（通过ChannelFuture）
    ChannelFuture register(Channel channel);

    ChannelFuture register(ChannelPromise promise);

    @Deprecated
    ChannelFuture register(Channel channel, ChannelPromise promise);
}

EventLoop

EventLoop继承关系

EventLoop继承了EventLoopGroup和OrderedEventExecutor。OrderedEventExecutor继承了EventExecutor接口未添加任何方法。

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public interface EventLoop extends OrderedEventExecutor, EventLoopGroup {
    @Override
    EventLoopGroup parent();
}

EventExecutor

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public interface EventExecutor extends EventExecutorGroup {
    
    @Override
    EventExecutor next();

    EventExecutorGroup parent();

    boolean inEventLoop();

    boolean inEventLoop(Thread thread);

    <V> Promise<V> newPromise();

    <V> ProgressivePromise<V> newProgressivePromise();

    <V> Future<V> newSucceededFuture(V result);

    <V> Future<V> newFailedFuture(Throwable cause);
}

ChannelFuture

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public interface ChannelFuture extends Future<Void> {

    /**
     * Returns a channel where the I/O operation associated with this
     * future takes place.
     */
    Channel channel();

    @Override
    ChannelFuture addListener(GenericFutureListener<? extends Future<? super Void>> listener);

    @Override
    ChannelFuture addListeners(GenericFutureListener<? extends Future<? super Void>>... listeners);

    @Override
    ChannelFuture removeListener(GenericFutureListener<? extends Future<? super Void>> listener);

    @Override
    ChannelFuture removeListeners(GenericFutureListener<? extends Future<? super Void>>... listeners);

    @Override
    ChannelFuture sync() throws InterruptedException;

    @Override
    ChannelFuture syncUninterruptibly();

    @Override
    ChannelFuture await() throws InterruptedException;

    @Override
    ChannelFuture awaitUninterruptibly();

    /**
     * Returns {@code true} if this {@link ChannelFuture} is a void future and so not allow to call any of the
     * following methods:
     * <ul>
     *     <li>{@link #addListener(GenericFutureListener)}</li>
     *     <li>{@link #addListeners(GenericFutureListener[])}</li>
     *     <li>{@link #await()}</li>
     *     <li>{@link #await(long, TimeUnit)} ()}</li>
     *     <li>{@link #await(long)} ()}</li>
     *     <li>{@link #awaitUninterruptibly()}</li>
     *     <li>{@link #sync()}</li>
     *     <li>{@link #syncUninterruptibly()}</li>
     * </ul>
     */
    boolean isVoid();
}

`