死锁，Java简单示例

死锁概念

多个线程互相持有对方等待的资源，导致这些线程全都阻塞。

Java简单示例

public class App {
private static final String LOCK_1 = "Lock1";
private static final String LOCK_2 = "Lock2";

public static void main(String[] args) {
new Thread1("Thread1").start();
new Thread2("Thread2").start();
    }

private static class Thread1 extends Thread {
        Thread1(String name) {
super(name);
        }

@Override
public void run() {
synchronized (LOCK_1) {
                holdingLock(LOCK_1);
                sleepForSomeTime(1);
                waitingLock(LOCK_2);
synchronized (LOCK_2) {
                    holdingLock(LOCK_2);
                }
                releaseLock(LOCK_2);
            }
            releaseLock(LOCK_1);
        }
    }


private static class Thread2 extends Thread {
        Thread2(String name) {
super(name);
        }

@Override
public void run() {
synchronized (LOCK_2) {
                holdingLock(LOCK_2);
                waitingLock(LOCK_1);
synchronized (LOCK_1) {
                    holdingLock(LOCK_1);
                }
                releaseLock(LOCK_1);
            }
            releaseLock(LOCK_2);
        }
    }
}

执行结果

Thread1 holding Lock1
Thread1 sleep 1s.
Thread2 holding Lock2
Thread2 waiting Lock1
Thread1 waiting Lock2

完整项目地址

https://git.coding.net/zhi-cike/dead-lock-demo.git

通过线程转存储查看是否存在死锁，当前为sun jdk使用jstack命令

利用ps查找上述代码执行线程PID，执行jstack PID，结果会直接输出到控制台
也可以输出到文件中jstack PID > dump.txt
执行结果如下