java的多线程学习，第五记

Posted 2021-01-28 TaylorLambert

 死锁问题；

public class DeadLock {

    //锁的嵌套 会出现死锁
    //1 尽量不要去写锁嵌套
    //2

    private static Object locka = new Object();
    private static Object lockb = new Object();

    public static void main(String[] args) {
        new DeadLock().deadLock();
    }

    private void deadLock() {
        Thread thread1 = new Thread(new Runnable() {
            @Override
            public void run() {
                synchronized (locka){
                    try {
                        System.out.println(Thread.currentThread().getName()+"获取A锁 ing~！");
                        Thread.sleep(500);
                        System.out.println(Thread.currentThread().getName()+"睡眠 500ms！");
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(Thread.currentThread().getName()+"需要B锁！！！");
                    synchronized (lockb){
                        System.out.println(Thread.currentThread().getName()+"B锁中！！！");
                    }
                }
            }
        },"thread1");

        Thread thread2 = new Thread(new Runnable() {
            @Override
            public void run() {
                synchronized (lockb){
                    try {
                        System.out.println(Thread.currentThread().getName()+"获取B锁 ing~！");
                        Thread.sleep(500);
                        System.out.println(Thread.currentThread().getName()+"睡眠 400ms！");
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(Thread.currentThread().getName()+"需要A锁！！");
                    synchronized (locka){
                        System.out.println(Thread.currentThread().getName()+"A锁中!");
                    }
                }
            }
        },"thread2");

        thread1.start();
        thread2.start();
    }

}

锁的嵌套 会出现死锁
1 尽量不要去写锁嵌套
2 锁嵌套的顺序
3 引入超时机制