Low thread wait and release troubles (wait/notify)

ClassThreadAextendsThread {Objectoanull; ThreadA (Objecto) {this. oao;} thread A executes the logic publicvoidrun () {thread synchronization region. You need to apply for the public data lock synchronized (oa) {System. out. p

Class ThreadA extends Thread {

// Public data area for Thread Synchronization

Object oa = null;

ThreadA (Object o ){

This. oa = o;

}

// Thread A execution Logic

Public void run (){

// Apply for a public data lock in the thread synchronization Area

Synchronized (oa ){

System. out. println ("ThreadA is running ......");

For (int I = 0; I <100; I ++ ){

System. out. println ("ThreadA value is" + I );

If (I = 50 ){

Try {

// The current thread waits

Thread. currentThread (). wait ();

} Catch (InterruptedException e ){

E. printStackTrace ();

}

} // If (I = 50)

} // For (int I)

}

}

}

/**

* Thread B: Wait for thread A to discard the lock, obtain and execute the lock, and then wake up thread.

*/

Class ThreadB extends Thread {

// Public data area for Thread Synchronization

Object ob = null;

ThreadB (Object o ){

This. ob = o;

}

// Thread B execution Logic

Public void run (){

// Apply for a public data lock in the thread synchronization Area

Synchronized (ob ){

System. out. println ("ThreadB is running ......");

For (int I = 0; I <50; I ++ ){

System. out. println ("ThreadB value is" + I );

}

　　

// Wake up the waiting thread

Notify ();

}

}

}

// Test

Public class ThreadTest {

Public static void main (String [] args ){

Object lock = new Object (); // public data Zone

ThreadA threada = new ThreadA (lock );

ThreadB threadb = new ThreadB (lock );

Threada. start (); // thread A executes

Threadb. start (); // thread B executes

}

} The program is very simple, that is, let threads A and B print alternately. However, two exceptions are thrown during running:

Exception in thread "Thread-0" java. lang. IllegalMonitorStateException: current thread not owner

Exception in thread "Thread-1" java. lang. IllegalMonitorStateException: current thread not owner

The problem lies in Thread. currentThread (). wait (); In ThreadA and running y () in ThreadB.

When beginners understand wait (), they all think it is blocking the current Thread, so Thread. currentThread (). wairt (); it makes sense. But I don't know if you have found that the wait () and notify () methods in the JDK class library are not in the Thread class, but in the Object. Let's take a closer look at the JDK documentation of the wait method:

Public final void wait () throws InterruptedException

Object (Java 2 Platform SE 6)