public class MyServer {
    public static void main(String[] args) {
        EventLoopGroup boseGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            // handler 只针对boseGroup
            // childHandler 经过boseGroup后再经过workerGroup
            serverBootstrap.group(boseGroup,workerGroup).channel(NioServerSocketChannel.class)
                    .childHandler(new MyServerInitializer());
            ChannelFuture channelFuture = serverBootstrap.bind(8899).sync();
            channelFuture.channel().closeFuture().sync();


        }catch (Exception e) {
            e.printStackTrace();
        }finally {
            boseGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

public class MyServerInitializer extends ChannelInitializer<SocketChannel> {
    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline pipeline = ch.pipeline();
        pipeline.addLast(new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE,0,4,0,4));
        pipeline.addLast(new LengthFieldPrepender(4));
        pipeline.addLast(new StringDecoder(CharsetUtil.UTF_8));
        pipeline.addLast(new StringEncoder(CharsetUtil.UTF_8));
        pipeline.addLast(new MyHttpServerHandler());
    }
}

public class MyHttpServerHandler extends SimpleChannelInboundHandler<String> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
        System.out.println(ctx.channel().remoteAddress() + ", " + msg);
        ctx.channel().writeAndFlush("from server "+ UUID.randomUUID());
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }
}

public class MyClient {
    public static void main(String[] args) {
        EventLoopGroup eventExecutors = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.group(eventExecutors).channel(NioSocketChannel.class)
                .handler(new MyClientInitializer());
            ChannelFuture localhost = bootstrap.connect("localhost", 8899).sync();
            localhost.channel().closeFuture().sync();

        }catch (Exception e) {
            e.printStackTrace();
        }finally {
            eventExecutors.shutdownGracefully();
        }
    }
}

public class MyClientInitializer extends ChannelInitializer<SocketChannel> {
    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline pipeline = ch.pipeline();
        pipeline.addLast(new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE,0,4,0,4));
        pipeline.addLast(new LengthFieldPrepender(4));
        pipeline.addLast(new StringDecoder(CharsetUtil.UTF_8));
        pipeline.addLast(new StringEncoder(CharsetUtil.UTF_8));
        pipeline.addLast(new MyClientHandler());
    }
}

public class MyClientHandler extends SimpleChannelInboundHandler<String> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
        System.out.println(ctx.channel().remoteAddress());
        System.out.println("client ouput: " + msg);
        ctx.channel().writeAndFlush("from client:"+ LocalDateTime.now());
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        ctx.writeAndFlush("来自于客户端的问候!");
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }
}

// node 数组
transient Node<K,V>[] table;
// Node结构
static class Node<K,V> implements Map.Entry<K,V> {
        final int hash;
        final K key;
        V value;
        Node<K,V> next;

        Node(int hash, K key, V value, Node<K,V> next) {
            this.hash = hash;
            this.key = key;
            this.value = value;
            this.next = next;
        }
}

/**
  * The load factor used when none specified in constructor.
*/
static final float DEFAULT_LOAD_FACTOR = 0.75f;

static final int TREEIFY_THRESHOLD = 8;

// 链表长度 > 8 并且数组长度小于64那么进行扩容，否则转为红黑树
static final int MIN_TREEIFY_CAPACITY = 64;

static final int TREEIFY_THRESHOLD = 8;

// 定义HashMap，初始大小可不写
HashMap<String, String> map = new HashMap<>(5);
// 存放值
map.put("test","name2");
// 取值
String test = map.get("test");

// 扩容操作 
final Node<K,V>[] resize() {
     // 数组
    Node<K,V>[] oldTab = table;
    // 旧数组的大小
    int oldCap = (oldTab == null) ? 0 : oldTab.length;
    // 扩容界限
    int oldThr = threshold;
    // 扩容后的大小，扩容后的界限
    int newCap, newThr = 0;
    if (oldCap > 0) {
        if (oldCap >= MAXIMUM_CAPACITY) {
            threshold = Integer.MAX_VALUE;
            return oldTab;
        }
        // 成倍的扩容,16 = 010000 << 1 --> 100000 = 32
        else if ((newCap = oldCap << 1) < MAXIMUM_CAPACITY &&
                 oldCap >= DEFAULT_INITIAL_CAPACITY)
            newThr = oldThr << 1; // double threshold
    }
    else if (oldThr > 0) // initial capacity was placed in threshold
        newCap = oldThr;
    else {               // zero initial threshold signifies using defaults
        // 初始化时的扩容操作
        newCap = DEFAULT_INITIAL_CAPACITY;
        newThr = (int)(DEFAULT_LOAD_FACTOR * DEFAULT_INITIAL_CAPACITY);
    }
    if (newThr == 0) {
        float ft = (float)newCap * loadFactor;
        newThr = (newCap < MAXIMUM_CAPACITY && ft < (float)MAXIMUM_CAPACITY ?
                  (int)ft : Integer.MAX_VALUE);
    }
    threshold = newThr;
    @SuppressWarnings({"rawtypes","unchecked"})
    Node<K,V>[] newTab = (Node<K,V>[])new Node[newCap];
    table = newTab;
    // 扩容后的数据迁移
    if (oldTab != null) {
        for (int j = 0; j < oldCap; ++j) {
            Node<K,V> e;
            if ((e = oldTab[j]) != null) {
                oldTab[j] = null;
                if (e.next == null)
                    newTab[e.hash & (newCap - 1)] = e;
                else if (e instanceof TreeNode)
                    ((TreeNode<K,V>)e).split(this, newTab, j, oldCap);
                else { // preserve order
                    // 扩容数据的低位链表,低位不变
                    Node<K,V> loHead = null, loTail = null;
                    // 扩容数据的高位链表，高位迁移
                    Node<K,V> hiHead = null, hiTail = null;
                    Node<K,V> next;
                    do {
                        next = e.next;
                        /**
                        * oldCap 16: 10000
                        * 假设e.hash = 9
                        * 第一次存放的位置:01001 & 01111 = 01001 = 9
                        * 为了保证扩容后用同样的操作取下标结果不会改变，也就是通过(n - 1) & hash还会取到e
                        * 扩容后：newCap = 32 = 100000
                        * 001001 & 011111 = 01001 = 9
                        * 所以对e这个数据不改变下标位置
                        * 01001 &
                        * 10000 = 0
                        **/
                        if ((e.hash & oldCap) == 0) {
                            if (loTail == null)
                                loHead = e;
                            else
                                loTail.next = e;
                            loTail = e;
                        }
                         /**
                        * oldCap 16: 10000
                        * 假设e.hash = 20
                        * 第一次存放的位置:10100 & 01111 = 00100 = 4
                        * 为了保证扩容后用同样的操作取下标结果不会改变，也就是通过(n - 1) & hash还会取到e
                        * 扩容后：newCap = 32 = 100000
                        * 010100 & 011111 = 010100 = 20
                        * 所以对e这个数据要改变下标位置为20
                        * 10100 &
                        * 10000 = 10000 != 0
                        * 所以要对该数据进行迁移，迁移坐标为：4 + 16(扩容的大小) = 20
                        **/
                        else {
                            if (hiTail == null)
                                hiHead = e;
                            else
                                hiTail.next = e;
                            hiTail = e;
                        }
                    } while ((e = next) != null);
                    if (loTail != null) {
                        loTail.next = null;
                        newTab[j] = loHead;
                    }
                    if (hiTail != null) {
                        hiTail.next = null;
                        newTab[j + oldCap] = hiHead;
                    }
                }
            }
        }
    }
    return newTab;
 }

public ThreadPoolExecutor(int corePoolSize,// 核心线程数
                              int maximumPoolSize,// 最大线程数
                              long keepAliveTime,// 超过核心线程数的其他线程存活时间
                              TimeUnit unit,// 超过核心线程数的其他线程存活时间单位
                              BlockingQueue<Runnable> workQueue,// 阻塞队列
                              ThreadFactory threadFactory,// 线程创建工厂
                              RejectedExecutionHandler handler) // 拒绝策略

public class SingletonDemo {
    private static SingletonDemo singletonDemo = new SingletonDemo();
    private static int count1;
    private static int count2 = 0;

    public SingletonDemo() {
        count1++;
        count2++;
        System.out.println("count1:" + count1);// 1
        System.out.println("count2:" + count2);// 2

    }
    public static void main(String[] args) {
        System.out.println("count1:" + count1);// 3
        System.out.println("count2:" + count2);// 4
    }
}