# Reactor单线程模式
EventLoopGroup eventGroup = new NioEventLoopGroup(1);
ServerBootstrap serverBootstrap = new ServerBootstrap();
serverBootstrap.group(eventGroup);
# 非主从Reactor多线程模式
EventLoopGroup eventGroup = new NioEventLoopGroup();
ServerBootstrap serverBootstrap = new ServerBootstrap();
I serverBootstrap.group eventGroup);
# 主从Reactor多线程模式
EventLoopGroup bossGroup = new NioEventLoopGroup();
EventLoopGroup workerGroup = new NioEventLoopGroup();
ServerBootstrap serverBootstrap = new ServerBootstrap();
serverBootstrap.group( bossGroup, workerGroup);

    public static SelectorProvider provider() {
        synchronized (lock) {
            if (provider != null)
                return provider;
            return AccessController.doPrivileged(
                new PrivilegedAction<SelectorProvider>() {
                    public SelectorProvider run() {
                            if (loadProviderFromProperty())
                                return provider;
                            if (loadProviderAsService())
                                return provider;
                            provider = sun.nio.ch.DefaultSelectorProvider.create();
                            return provider;
                        }
                    });
        }
    }