5.1、Thread和Object类中的重要方法

Thread和Object类中的重要方法

一、 方法概览

/**
 * 描述：演示打印main, Thread-0, Thread-1
 */
public class CurrentThread implements Runnable {

    public static void main(String[] args) {
        new CurrentThread().run();
        new Thread(new CurrentThread()).start();
        new Thread(new CurrentThread()).start();
    }

    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName());
    }

    /**
     * 输出：
     * main
     * Thread-0
     * Thread-1
     *
     */
}

二、wait/notify/notifyAll

2.1 基本用法

作用/用法：阻塞阶段、唤醒阶段、遇到中断

/**
 * 描述：展示wait和notify的基本用法 1. 研究代码执行顺序 2. 证明wait释放锁
 */
public class Wait {

    public static Object object = new Object();

    static class Thread1 extends Thread {

        @Override
        public void run() {
            synchronized (object) {
                System.out.println(Thread.currentThread().getName() + "开始执行了");
                try {
                    object.wait();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("线程" + Thread.currentThread().getName() + "获取到了锁。");
            }
        }
    }

    static class Thread2 extends Thread {

        @Override
        public void run() {
            synchronized (object) {
                object.notify();
                System.out.println("线程" + Thread.currentThread().getName() + "调用了notify()");
            }
        }
    }

    public static void main(String[] args) throws InterruptedException {
        Thread1 thread1 = new Thread1();
        Thread2 thread2 = new Thread2();
        thread1.start();
        Thread.sleep(200);
        thread2.start();
    }

    /**
     * 展示wait和notify的基本用法 1. 研究代码执行顺序 2. 证明wait释放锁
     *
     * 输出：
     * Thread-0开始执行了
     * 线程Thread-1调用了notify()
     * 线程Thread-0获取到了锁。
     */
}

/**
 * 描述：3个线程，线程1和线程2首先被阻塞，线程3唤醒它们。notify, notifyAll。 start先执行不代表线程先启动。
 */
public class WaitNotifyAll implements Runnable {

    private static final Object resourceA = new Object();


    public static void main(String[] args) throws InterruptedException {
        Runnable r = new WaitNotifyAll();
        Thread threadA = new Thread(r);
        Thread threadB = new Thread(r);
        Thread threadC = new Thread(new Runnable() {
            @Override
            public void run() {
                synchronized (resourceA) {
                    resourceA.notifyAll();
//                    resourceA.notify();
                    System.out.println("ThreadC notified.");
                }
            }
        });
        threadA.start();
        threadB.start();
//        Thread.sleep(200);
        threadC.start();
    }
    @Override
    public void run() {
        synchronized (resourceA) {
            System.out.println(Thread.currentThread().getName()+" got resourceA lock.");
            try {
                System.out.println(Thread.currentThread().getName()+" waits to start.");
                resourceA.wait();
                System.out.println(Thread.currentThread().getName()+"'s waiting to end.");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
    /**
     *3个线程，线程1和线程2首先被阻塞，线程3唤醒它们。notify, notifyAll。 start先执行不代表线程先启动。
     *
     * 输出：
     *
     * Thread-0 got resourceA lock.
     * Thread-0 waits to start.
     * ThreadC notified.
     * Thread-1 got resourceA lock.
     * Thread-1 waits to start.
     * Thread-0's waiting to end.
     * ...
     *
     */
}

wait只释放当前的那把锁

/**
 * 描述：证明wait只释放当前的那把锁
 */
public class WaitNotifyReleaseOwnMonitor {

    private static volatile Object resourceA = new Object();
    private static volatile Object resourceB = new Object();

    public static void main(String[] args) {
        Thread thread1 = new Thread(new Runnable() {
            @Override
            public void run() {
                synchronized (resourceA) {
                    System.out.println("ThreadA got resourceA lock.");
                    synchronized (resourceB) {
                        System.out.println("ThreadA got resourceB lock.");
                        try {
                            System.out.println("ThreadA releases resourceA lock.");
                            resourceA.wait();

                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                }
            }
        });

        Thread thread2 = new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                synchronized (resourceA) {
                    System.out.println("ThreadB got resourceA lock.");
                    System.out.println("ThreadB tries to resourceB lock.");

                    synchronized (resourceB) {
                        System.out.println("ThreadB got resourceB lock.");
                    }
                }
            }
        });

        thread1.start();
        thread2.start();
    }
    /**
     * 证明wait只释放当前的那把锁
     * 
     * 输出：
     *
     * ThreadA got resourceA lock.
     * ThreadA got resourceB lock.
     * ThreadA releases resourceA lock.
     * ThreadB got resourceA lock.
     * ThreadB tries to resourceB lock.
     * ...
     *
     */
}