java.lang.IllegalMonitorStateExc

1.报错信息

2020-10-22 17:16:40.044 30626-30672/com.example.uxin.myapplication E/AndroidRuntime: FATAL EXCEPTION: Thread-2
    Process: com.example.uxin.myapplication, PID: 30626
    java.lang.IllegalMonitorStateException: object not locked by thread before wait()
        at java.lang.Object.wait(Native Method)
        at threadtest.Thread1.run(Thread1.java:35)
2020-10-22 17:16:40.045 30626-30672/com.example.uxin.myapplication E/AbstractTracker: Can't create handler inside thread that has not called Looper.prepare()
2020-10-22 17:16:40.049 30626-30672/com.example.uxin.myapplication E/AbstractTracker: mTrackerAsyncQueryHandler is null

2.代码

public class Thread1 extends Thread{

    private Object object = new Object();
    @Override
    public void run() {
        super.run();
        System.out.println("thread1");
        System.out.println(this.getState());
        System.out.println(this.getThreadGroup().getName());
        Log.i("cyp", "run: "+this.getThreadGroup().activeCount());
        synchronized (object) {
            try {
                wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

}

调用代码

 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_thread_test);
       // 创建线程并启动
        thread1 = new Thread1(lockObject);
        thread1.start();
        Log.i(TAG, "thread1 "+thread1.getState());
    }

3。问题原因：在Thead1中直接调用wait方法，是调用的Thread1的的wait方法，而不是synchronized锁的对象即object的wait方法，应该调用object的wait方法，notify/notifyAll方法同样用法
4.代码修改

public class Thread1 extends Thread{

    private Object object = new Object();
    @Override
    public void run() {
        super.run();
        System.out.println("thread1");
        System.out.println(this.getState());
        System.out.println(this.getThreadGroup().getName());
        Log.i("cyp", "run: "+this.getThreadGroup().activeCount());
        synchronized (object) {
            try {
// 用synchronized锁定的锁对象来调用wait方法
                object.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

}

5.总结：
要保证你调用的wait、notify ，notifyAll的对象，是你synchronized 的对象。

重点：wait，notify，notifyAll这几个方法必须在synchronized即有锁状态下调用，任何对象上调用这些方法的当前线程都应该具有对象监视器，否则它将抛出java.lang.IllegalMonitorStateException