死锁

死锁demo

package org.example;

public class Main {
    private static Object resource1 = new Object();//资源 1
    private static Object resource2 = new Object();//资源 2

    public static void main(String[] args) {
        new Thread(() -> {
            synchronized (resource1) {
                System.out.println(Thread.currentThread().getName() + " get resource1");
                try {
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println(Thread.currentThread().getName() + " waiting get resource2");
                synchronized (resource2) {
                    System.out.println(Thread.currentThread().getName() + " get resource2");
                }
            }
        }, "线程 1").start();

        new Thread(() -> {
            synchronized (resource2) {
                System.out.println(Thread.currentThread().getName() + " get resource2");
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println(Thread.currentThread().getName() + " waiting get resource1");
                synchronized (resource1) {
                    System.out.println(Thread.currentThread().getName() + " get resource1");
                }
            }
        }, "线程 2").start();
    }
}

解决死锁的方法

要解决这个死锁，需要：

1. 统一锁的获取顺序：

// 两个线程都按相同顺序获取锁
synchronized (resource1) {
    synchronized (resource2) {
        // 业务逻辑
    }
}

2. 使用超时机制：

if (lock1.tryLock(1000, TimeUnit.MILLISECONDS)) {
    try {
        if (lock2.tryLock(1000, TimeUnit.MILLISECONDS)) {
            // 业务逻辑
        }
    } finally {
        lock1.unlock();
    }
}