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 Lock1Thread1 sleep 1s.Thread2 holding Lock2Thread2 waiting Lock1Thread1 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