多线程 wait() 通知()

Question

Can someone please tell me whats wrong with the current program

/*
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package evenodd;

import java.util.logging.Level;
import java.util.logging.Logger;

public class EvenOdd {

    public static Integer i;
    public static Integer y;

    public static void main(String[] args) {
        EvenOdd eo = new EvenOdd();
        EvenThread et = new EvenThread(eo);
        et.setName("EvenThread");
        OddThread ot = new OddThread(eo);
        ot.setName("OddThread");
        et.start();
        ot.start();

    }
}
class EvenThread extends Thread{
    EvenOdd eo;
    public EvenThread(EvenOdd eo)
    {
        this.eo=eo;
    }
    public void run()
    {

        System.out.println("inside run "+Thread.currentThread().getName());
        if(eo.y==null)
        {
        try {
            Thread.sleep(200);
        } catch (InterruptedException ex) {
            Logger.getLogger(EvenThread.class.getName()).log(Level.SEVERE, null, ex);
        }
        }

        synchronized(eo)
        {

       if(eo.y==null)
       {
           eo.y=2;
           System.out.println("Even Number " + eo.y);

       }
       else if(eo.y!=null)
       {
           System.out.println("Even Number " + eo.y+2);
       }
       System.out.println("notifying "+Thread.currentThread().getName());
       eo.notify();

    }
    }

}

class OddThread extends Thread{
     EvenOdd eo;
    public OddThread(EvenOdd eo)
    {
        this.eo=eo;
    }

   public void run()
   {

       System.out.println("inside run "+Thread.currentThread().getName());
       synchronized(eo)
       {

       if(eo.i==null)
       {
           eo.i=1;
           System.out.println("Odd NUmber " + eo.i);
       }
       else if(eo.i!=null)
       {
           System.out.println("Odd NUmber " + eo.i+2);
       }
         try {
             System.out.println("waiting "+Thread.currentThread().getName());
             eo.wait();
         } catch (InterruptedException ex) {
             Logger.getLogger(OddThread.class.getName()).log(Level.SEVERE, null, ex);
         }
   }
   }
}

When EvenThread notifies why control is not going to OddThread. I am using teo threads to print odd and even numbers, one thread to print odd numbers and one thread to print even numbers. First i am trying to print 1 and 2 and later increment both values by 2.

Answer 1

如果您的代码已经通过了添加 2 的点并且您没有任何循环返回到那里，您如何期望添加 2？

Answer 2

Your code does exactly what you've coded it to do.

1. You start both threads
2. even goes to sleep for 200 ms
3. odd initializes the shared variable to 1, then goes to sleep waiting for even
4. even wakes up, increments the shared variable to 2, notifies, and then exits
5. odd wakes up by the notification, then exits.

If you want to endlessly print numbers, you need to loop in both threads and restructure your code a little.