使用Jconsole分析死锁

我正在运行一个导致死锁的简单程序.

    final  String resource1 = "santanu";
    final String resource2 = "sahoo";
     System.out.println(Integer.toHexString(resource1.hashCode())    );
     System.out.println(Integer.toHexString(resource2.hashCode()) );

    Thread t1 = new Thread(){

        public void run()
        {
            synchronized (resource1) {
                System.out.println("Thread 1: locked resource 1");  
                try {

                    Thread.sleep(200);

                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                synchronized (resource2) {
                     System.out.println("Thread 1: locked resource 2");     
                }               
            }
        }
    };
    Thread t2 = new Thread(){
        public void run()
        {
            synchronized (resource2) {
                try {
                     System.out.println("Thread 2: locked resource 2");  
                    Thread.sleep(200);
                } catch (InterruptedException e) {
                                            e.printStackTrace();
                }
                synchronized (resource1) {
                     System.out.println("Thread 2: locked resource 1");  
                }
            }
        }
    };

    t1.start();
    t2.start();

以下是预期产量

6f3700d4      
6823b3a        
Thread 1: locked resource 1
Thread 2: locked resource 2

现在我解雇了jps命令并找到了这个java程序的PID并使用了jconsole< pid>命令查看死锁.

下面是jconsole中的堆栈跟踪

Name: Thread-1
State: BLOCKED on java.lang.String@4ad61aef owned by: Thread-0
Total blocked: 1  Total waited: 1

Stack trace: 
 com.cmc.santanusol$2.run(santanusol.java:49)
   - locked java.lang.String@4406cef4

现在我的问题是为什么jconsole stacktrace显示不同对象的HexString(java.lang.String @)与我在前两个sysout中打印的值相比较？

更确切地说,为什么6f3700d4和6823b3a值没有出现在jconsole输出中？

解决方法:

问题是String覆盖了hashCode.使用

System.out.println(Integer.toHexString(System.identityHashCode(resource1)));
System.out.println(Integer.toHexString(System.identityHashCode(resource2)));

用于调试.

背景：对象返回

getClass().getName() + "@" + Integer.toHexString(hashCode());

在toString中,但String和其他类重写toString(使用在此上下文中没有帮助的字符串),因此JConsole显示原始Object.toString显示的信息.

标签：java,multithreading,deadlock,jconsole
来源： https://codeday.me/bug/20190706/1399070.html