Hey,buddy，写个死锁看看

诺，写给你看

public class LockInterruptly extends Thread{
    public static ReentrantLock lock1=new ReentrantLock();
    public static ReentrantLock lock2=new ReentrantLock();
    int flag;
    public LockInterruptly(String name,int flag){
        super.setName(name);
        this.flag=flag;
    }
    //在线程任务里构造死锁
    @Override
    public void run(){
        try{
            if(flag==1){
                lock1.lockInterruptibly();
                try{
                    Thread.sleep(500);
                }catch (Exception e){
                    e.printStackTrace();
                }
                lock2.lockInterruptibly();
            }else{
                lock2.lockInterruptibly();
                try{
                    Thread.sleep(500);
                }catch (Exception e){
                    e.printStackTrace();
                }
                lock1.lockInterruptibly();
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            if(lock1.isHeldByCurrentThread()){
                lock1.unlock();
            }
            if(lock2.isHeldByCurrentThread()){
                lock2.unlock();
            }
            System.out.println(Thread.currentThread().getId()+":线程退出");
        }
    }

    public static void main(String[] args) throws InterruptedException {
        LockInterruptly t1=new LockInterruptly("LockInterrupt1",1);
        LockInterruptly t2=new LockInterruptly("LockInterrupt2",2);
        t1.start();
        t2.start();
        Thread.sleep(1000);

    }
}

怎么看死锁呢？先jps找到死锁的进程ID，如下

E:\temp1\test>jps
5568 LockInterruptly
18804 Launcher
3940 Jps
15000

可以找到对应的ID为5568
然后jstack指令

jstack -l 5568

可以看到下面的信息提示：

Java stack information for the threads listed above:
===================================================
"LockInterrupt2":
        at sun.misc.Unsafe.park(Native Method)
        - parking to wait for  <0x00000000d62d3268> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)
        at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireInterruptibly(AbstractQueuedSynchronizer.java:897)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireInterruptibly(AbstractQueuedSynchronizer.java:1222)
        at java.util.concurrent.locks.ReentrantLock.lockInterruptibly(ReentrantLock.java:335)
        at com.example.demo.plaintest.LockInterruptly.run(LockInterruptly.java:32)
"LockInterrupt1":
        at sun.misc.Unsafe.park(Native Method)
        - parking to wait for  <0x00000000d62d3298> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)
        at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireInterruptibly(AbstractQueuedSynchronizer.java:897)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireInterruptibly(AbstractQueuedSynchronizer.java:1222)
        at java.util.concurrent.locks.ReentrantLock.lockInterruptibly(ReentrantLock.java:335)
        at com.example.demo.plaintest.LockInterruptly.run(LockInterruptly.java:24)

Found 1 deadlock.