死锁了

代码

public class MonitorThreadDeadLockTest {
    static class SynAddRunable implements Runnable{
        int a,b;
        public SynAddRunable(int a,int b){
            this.a = a;
            this.b = b;
        }
        @Override
        public void run() {
            synchronized (Integer.valueOf(a)){
                synchronized (Integer.valueOf(b)){
                    System.out.println(a + b);
                }
            }
        }
    }
    public static void main(String[] args) {
        for (int i = 0; i < 1000; i++) {
            new Thread(new SynAddRunable(1,2)).start();
            new Thread(new SynAddRunable(2,1)).start();
        }
    }
}

可能的现象

1.大量block的线程,可能很多对象都要拿那把锁.

检测

1.拿到异常的java进程　top,sar,jps等.公司的监控系统都能看出来.

top

2.查看其线程dump

sudo  -u tomcat jstack 6123 > stack.log

3.大量线程blocked,并发现deadlock

dead_lock

4.卧槽，死锁了

工作遇到的

//todo