死锁例子

r囧r小猫 2022-12-12 02:16 191阅读 0赞

/**
     * 必定发生死锁的情况
     */
    public class MustDeadLock implements Runnable {
        private final Object lockA;
        private final Object lockB;
        public MustDeadLock(Object lockA, Object lockB) {
            this.lockA = lockA;
            this.lockB = lockB;
        }
        @Override
        public void run() {
            System.out.println(Thread.currentThread().getName() + "进入了run方法...");
            synchronized (lockA) {
                try {
                    TimeUnit.SECONDS.sleep(2);
                } catch (InterruptedException ignored) {}
                System.out.println(Thread.currentThread().getName() + "持有" + lockA + ",尝试获得" + lockB);
                synchronized (lockB) {
                    System.out.println(Thread.currentThread().getName() + "成功拿到两把锁");
                }
            }
        }
        public static void main(String[] args) {
            Object lockA = new Object();
            Object lockB = new Object();
            new Thread(new MustDeadLock(lockA, lockB), "AAA").start();
            new Thread(new MustDeadLock(lockB, lockA), "BBB").start();
        }
    }

/**
     * 必定发生死锁的情况
     */
    public class MustDeadLock implements Runnable {
        static final Object LOCK_A = new Object();
        static final Object LOCK_B = new Object();
        @Override
        public void run() {
            System.out.println(Thread.currentThread().getName() + "进入了run方法...");
            if ("A".equals(Thread.currentThread().getName())) {
                synchronized (LOCK_A) {
                    try {
                        Thread.sleep(500);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    synchronized (LOCK_B) {
                        System.out.println("线程A成功拿到两把锁");
                    }
                }
            }
            if ("B".equals(Thread.currentThread().getName())) {
                synchronized (LOCK_B) {
                    try {
                        Thread.sleep(500);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    synchronized (LOCK_A) {
                        System.out.println("线程B成功拿到两把锁");
                    }
                }
            }
        }
        public static void main(String[] args) {
            MustDeadLock run = new MustDeadLock();
            Thread t1 = new Thread(run, "A");
            Thread t2 = new Thread(run, "B");
            t1.start();
            t2.start();
        }
    }