int priority = i < 5 ? Thread.MIN_PRIORITY : Thread.MAX_PRIORITY;
thread.setPriority(priority);

public class Daemon {
    public static void main(String[] args) {
        Thread thread = new Thread(new DaemonRunner());
        thread.setDaemon(true);
        thread.start();
    }

    static class DaemonRunner implements Runnable {
        @Override
        public void run() {
            try {
                SleepUtils.second(100);
            } finally {
                System.out.println("DaemonThread finally run.");
            }
        }
    }
}

public class Shutdown {
    public static void main(String[] args) throws Exception {
        /**
         * 方式一
         */
        Runner one = new Runner();
        Thread countThread = new Thread(one, "CountThread");
        countThread.start();
        // 睡眠1秒，main线程对CountThread进行中断，使CountThread能够感知中断而结束
        TimeUnit.SECONDS.sleep(1);
        countThread.interrupt();
        /**
         * 方式二
         */
        Runner two = new Runner();
        countThread = new Thread(two, "CountThread");
        countThread.start();
        // 睡眠1秒，main线程对Runner two进行取消，使CountThread能够感知on为false而结束
        TimeUnit.SECONDS.sleep(1);
        two.cancel();
    }

    private static class Runner implements Runnable {
        private long i;
        private volatile boolean on = true;

        @Override
        public void run() {
            while (on && !Thread.currentThread().isInterrupted()) {
                i++;
            }
            System.out.println("Count i = " + i);
        }

        public void cancel() {
            on = false;
        }
    }
}

public class WaitNotify {
    static boolean flag = true;
    static Object lock = new Object();

    public static void main(String[] args) throws Exception {
        Thread waitThread = new Thread(new Wait(), "WaitThread");
        waitThread.start();
        TimeUnit.SECONDS.sleep(1);

        Thread notifyThread = new Thread(new Notify(), "NotifyThread");
        notifyThread.start();
    }

    static class Wait implements Runnable {
        public void run() {
            // 加锁，拥有lock的Monitor
            synchronized (lock) {
                // 当条件不满足时，继续wait，同时释放了lock的锁
                while (flag) {
                    try {
                        System.out.println(Thread.currentThread() + " flag is true. wait @ "
                                + new SimpleDateFormat("HH:mm:ss").format(new Date()));
                        lock.wait();
                    } catch (InterruptedException e) {
                    }
                }
                // 条件满足时，完成工作
                System.out.println(Thread.currentThread() + " flag is false. running @ "
                        + new SimpleDateFormat("HH:mm:ss").format(new Date()));
            }
        }
    }

    static class Notify implements Runnable {
        public void run() {
            // 加锁，拥有lock的Monitor
            synchronized (lock) {
                // 获取lock的锁，然后进行通知，通知时不会释放lock的锁，
                // 直到当前线程释放了lock后，WaitThread才能从wait方法中返回
                System.out.println(Thread.currentThread() + " hold lock. notify @ " + new SimpleDateFormat("HH:mm:ss").format(new Date()));
                lock.notifyAll();
                flag = false;
                SleepUtils.second(5);
            }
            // 再次加锁
            synchronized (lock) {
                System.out.println(Thread.currentThread() + " hold lock again. sleep @ "
                        + new SimpleDateFormat("HH:mm:ss").format(new Date()));
                SleepUtils.second(5);
            }
        }
    }
}

public class Piped {
    public static void main(String[] args) throws Exception {
        PipedWriter out = new PipedWriter();
        PipedReader in = new PipedReader();
        // 将输出流和输入流进行连接，否则在使用时会抛出IOException
        out.connect(in);
        Thread printThread = new Thread(new Print(in), "PrintThread");
        printThread.start();
        int receive;
        try {
            while ((receive = System.in.read()) != -1)
                out.write(receive);
        } finally {
            out.close();
        }
    }

    static class Print implements Runnable {
        private PipedReader in;

        public Print(PipedReader in) {
            this.in = in;
        }
        
        public void run() {
            int receive;
            try {
                while ((receive = in.read()) != -1)
                    System.out.print((char) receive);
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
    }
}

public class Profiler {
    // 第一次get()方法调用时会进行初始化（如果set方法没有调用），每个线程会调用一次
    private static final ThreadLocal<Integer> VALUE_THREADLOCAL = ThreadLocal.withInitial(() -> new Random().nextInt());

    public static void set() {
        VALUE_THREADLOCAL.set(new Random().nextInt());
    }

    public static String get() {
        return VALUE_THREADLOCAL.get().toString();
    }

    public static void main(String[] args) throws Exception {
        new ThreadTest().run();
        new ThreadTest().run();
        new ThreadTest().run();
    }
}

class ThreadTest extends Thread {
    @Override
    public void run() {
        Profiler.set();
        System.out.println(Profiler.get());
    }
}

public synchronized Object get(long mills) throws InterruptedException {
  long future = System.currentTimeMillis();
  long remaining = mills;
  // 当前超时大于0 并且 返回值不满足要求
  Object result = null;
  while (result == null && remaining > 0) {
    wait(remaining);
    remaining = future - System.currentTimeMillis();
  }
  return result;
}

public class ConnectionPool {

    private LinkedList<Connection> pool = new LinkedList<>();

    public ConnectionPool(int initialSize) {
        if (initialSize > 0) {
            for (int i = 0; i < initialSize; i++) {
                pool.addLast(ConnectionDriver.createConnection());
            }
        }
    }

    public void releaseConnection(Connection connection) {
        if (connection != null) {
            synchronized (pool) {
                // 添加后需要进行通知，这样其他消费者能够感知到链接池中已经归还了一个链接
                pool.addLast(connection);
                pool.notifyAll();
            }
        }
    }

    // 在mills内无法获取到连接，将会返回null
    public Connection fetchConnection(long mills) throws InterruptedException {
        synchronized (pool) {
            // 完全超时
            if (mills <= 0) {
                while (pool.isEmpty()) {
                    pool.wait();
                }
                return pool.removeFirst();
            } else {
                long future = System.currentTimeMillis() + mills;
                long remaining = mills;
                while (pool.isEmpty() && remaining > 0) {
                    pool.wait(remaining);
                    remaining = future - System.currentTimeMillis();
                }
                Connection result = null;
                if (!pool.isEmpty()) {
                    result = pool.removeFirst();
                }
                return result;
            }
        }
    }
}

public class ConnectionDriver {
    static class ConnectionHandler implements InvocationHandler {
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
            if (method.getName().equals("commit")) {
                TimeUnit.MILLISECONDS.sleep(100);
            }
            return null;
        }
    }

    // 创建一个Connection的代理，在commit时休眠1秒
    public static final Connection createConnection() {
        return (Connection) Proxy.newProxyInstance(ConnectionDriver.class.getClassLoader(), new Class<?>[]{Connection.class},
                new ConnectionHandler());
    }
}

public class ConnectionPoolTest {
    static ConnectionPool pool = new ConnectionPool(10);
    // 保证所有ConnectionRunner能够同时开始
    static CountDownLatch start = new CountDownLatch(1);
    // main线程将会等待所有ConnectionRunner结束后才能继续执行
    static CountDownLatch end;

    public static void main(String[] args) throws Exception {
        // 线程数量，可以线程数量进行观察
        int threadCount = 50;
        end = new CountDownLatch(threadCount);
        int count = 20;
        AtomicInteger got = new AtomicInteger();
        AtomicInteger notGot = new AtomicInteger();
        for (int i = 0; i < threadCount; i++) {
            Thread thread = new Thread(new ConnetionRunner(count, got, notGot), "ConnectionRunnerThread");
            thread.start();
        }
        start.countDown();
        end.await();
        System.out.println("total invoke: " + (threadCount * count));
        System.out.println("got connection:  " + got);
        System.out.println("not got connection " + notGot);
    }

    static class ConnetionRunner implements Runnable {
        int count;
        AtomicInteger got;
        AtomicInteger notGot;

        public ConnetionRunner(int count, AtomicInteger got, AtomicInteger notGot) {
            this.count = count;
            this.got = got;
            this.notGot = notGot;
        }

        public void run() {
            try {
                start.await();
            } catch (Exception ex) {
                ex.printStackTrace();
            }
            while (count > 0) {
                try {
                    // 从线程池中获取连接，如果1000ms内无法获取到，将会返回null
                    // 分别统计连接获取的数量got和未获取到的数量notGot
                    Connection connection = pool.fetchConnection(1000);
                    if (connection != null) {
                        try {
                            connection.createStatement();
                            connection.commit();
                        } finally {
                            pool.releaseConnection(connection);
                            got.incrementAndGet();
                        }
                    } else {
                        notGot.incrementAndGet();
                    }
                } catch (Exception ex) {
                    ex.printStackTrace();
                } finally {
                    count--;
                }
            }
            end.countDown();
        }
    }
}

public interface ThreadPool<Job extends Runnable> {
    // 执行一个Job，这个Job需要实现Runnable
    void execute(Job job);
    // 关闭线程池
    void shutdown();
    // 增加工作者线程
    void addWorkers(int num);
    // 减少工作者线程
    void removeWorker(int num);
    // 得到正在等待执行的任务数量
    int getJobSize();
}

public class DefaultThreadPool<Job extends Runnable> implements ThreadPool<Job> {
    // 线程池最大限制数
    private static final int MAX_WORKER_NUMBERS = 10;
    // 线程池默认的数量
    private static final int DEFAULT_WORKER_NUMBERS = 5;
    // 线程池最小的数量
    private static final int MIN_WORKER_NUMBERS = 1;
    // 这是一个工作列表，将会向里面插入工作
    private final LinkedList<Job> jobs = new LinkedList<>();
    // 工作者列表
    private final List<Worker> workers = Collections.synchronizedList(new ArrayList<Worker>());
    // 工作者线程的数量
    private int workerNum = DEFAULT_WORKER_NUMBERS;
    // 线程编号生成
    private AtomicLong threadNum = new AtomicLong();

    public DefaultThreadPool() {
        initializeWokers(DEFAULT_WORKER_NUMBERS);
    }

    public DefaultThreadPool(int num) {
        workerNum = num > MAX_WORKER_NUMBERS ? MAX_WORKER_NUMBERS : num < MIN_WORKER_NUMBERS ? MIN_WORKER_NUMBERS : num;
        initializeWokers(workerNum);
    }

    public void execute(Job job) {
        if (job != null)
            // 添加一个工作，然后进行通知
            synchronized (jobs) {
                jobs.addLast(job);
                jobs.notify();
            }
    }

    public void shutdown() {
        for (Worker worker : workers)
            worker.shutdown();
    }

    public void addWorkers(int num) {
        synchronized (jobs) {
            // 限制新增的Worker数量不能超过最大值
            if (num + this.workerNum > MAX_WORKER_NUMBERS)
                num = MAX_WORKER_NUMBERS - this.workerNum;
            initializeWokers(num);
            this.workerNum += num;
        }
    }

    public void removeWorker(int num) {
        synchronized (jobs) {
            if (num >= this.workerNum)
                throw new IllegalArgumentException("beyond workNum");
            // 按照给定的数量停止Worker
            int count = 0;
            while (count < num) {
                workers.get(count).shutdown();
                count++;
            }
            this.workerNum -= count;
        }
    }

    public int getJobSize() {
        return jobs.size();
    }

    // 初始化线程工作者
    private void initializeWokers(int num) {
        for (int i = 0; i < num; i++) {
            Worker worker = new Worker();
            workers.add(worker);
            Thread thread = new Thread(worker, "ThreadPool-Worker-" + threadNum.incrementAndGet());
            thread.start();
        }
    }

    // 工作者，负责消费任务
    class Worker implements Runnable {
        // 是否工作
        private volatile boolean running = true;

        public void run() {
            while (running) {
                Job job;
                synchronized (jobs) {
                    // 如果工作者列表是空的，那么就wait
                    while (jobs.isEmpty()) {
                        try {
                            jobs.wait();
                        } catch (InterruptedException ex) {
                            // 感知到外部对WorkerThread的中断操作，返回
                            Thread.currentThread().interrupt();
                            return;
                        }
                    }
                    // 取出一个Job
                    job = jobs.removeFirst();
                }
                if (job != null)
                    try {
                        job.run();
                    } catch (Exception ex) {
                        // 忽略Job执行中的Exception
                    }
            }
        }
        
        public void shutdown() {
            running = false;
        }
    }
}

public class Cache {
    private static final Map<String, Object>    map = new HashMap<>();
    private static final ReentrantReadWriteLock rwl = new ReentrantReadWriteLock();
    private static final Lock                   r   = rwl.readLock();
    private static final Lock                   w   = rwl.writeLock();
  
    // 获取key对应的value
    public static final Object get(String key) {
        r.lock();
        try {
            return map.get(key);
        } finally {
            r.unlock();
        }
    }
  
    // 设置key对应的value，并返回旧的value
    public static final Object put(String key, Object value) {
        w.lock();
        try {
            return map.put(key, value);
        } finally {
            w.unlock();
        }
    }
  
    // 清空所有内容
    public static final void clear() {
        w.lock();
        try {
            map.clear();
        } finally {
            w.unlock();
        }
    }
}

public class ConditionUseCase {
    Lock      lock      = new ReentrantLock();
    Condition condition = lock.newCondition();

    public void conditionWait() throws InterruptedException {
        lock.lock();
        try {
          	// 释放锁并在此等待
            condition.await();
        } finally {
            lock.unlock();
        }
    }

    public void conditionSignal() throws InterruptedException {
        lock.lock();
        try {
            condition.signal();
        } finally {
            lock.unlock();
        }
    }
}

Path source = Paths.get("Netty学习/netty-demo/data.txt");