重置搜索 java并发编程——死锁现象演示与排查

待我称王封你为后i 2022-12-10 02:24 80阅读 0赞

# 死锁现象演示与排查 #

在IDE工具运行以下代码，发现没有退出，点击`DeadLockDemo`类，右键，`open in Terminal`，打开控制台。

package thread;
    
    import java.util.concurrent.TimeUnit;
    
    public class DeadLockDemo { 
        public static void main(String[] args) { 
            String lockA = "lockA";
            String lockB = "lockB";
            new Thread(new HoldLockThread(lockA, lockB), "ThreadA").start();
            new Thread(new HoldLockThread(lockB, lockA), "ThreadB").start();
        }
    }
    
    class HoldLockThread implements Runnable { 
        private String lockA;
        private String lockB;
    
        public HoldLockThread(String lockA, String lockB) { 
            this.lockA = lockA;
            this.lockB = lockB;
        }
    
        @Override
        public void run() { 
            synchronized (lockA) { 
                System.out.println(Thread.currentThread().getName() + "\t自己持有：" + lockA + "\t尝试获取：" + lockB);
                try { 
                    TimeUnit.SECONDS.sleep(2);
                } catch (Exception e) { 
                    e.printStackTrace();
                }
                synchronized (lockB) { 
                    System.out.println(Thread.currentThread().getName() + "\t自己持有：" + lockB + "\t尝试获取：" + lockA);
                }
            }
        }
    }

输入框`jps -l`，查看线程列表，输入`jstack 线程ID`。

jps -l

![jps命令][jps]

jstack 7104

![在这里插入图片描述][20200923142704168.png]  
这个时候，发现了死锁。`Found 1 deadlock.`。

[jps]: /images/20221123/1219f62799e0479e8aac4e219c7599d9.png
[20200923142704168.png]: /images/20221123/5a128c2f93aa415e81a9fdcb7598bdcc.png