Question

After execution the below code and throwing IllegalMonitorStateException
exception. I am getting error as:

java.lang.IllegalMonitorStateException
    at java.lang.Object.notify(Native Method)
    at com.blt.ThreadExample.main(ThreadExample.java:21)

I am new in multithreading, I want to use wait() and notify() in the code.

package com.blt;



public class ThreadExample implements Runnable {
    public static void main(String args[])
    {


        System.out.println("A");
        Thread T = new Thread(new ThreadExample());
        Thread T1 = new Thread(new ThreadExample());

        System.out.println("B");
        try
        {
        T.setName("thread 1");
        T.start();
        T1.setName("thread 2");
        System.out.println("C");
        T.notify();

        System.out.println("D");
        T1.start();
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }
    }


        public  void run()
{


            synchronized(ThreadExample.class)
            {


        for(int i=0; i<5; i++)
    {

        try
        {
            Thread.currentThread().wait(400);
         System.out.println("Inside run=>"+Thread.currentThread().getName());
         Thread.currentThread().sleep(2000);




        }
         catch(Exception e)
        {
            e.printStackTrace();
        }
      }  
}
}
}

Answer 1

Try this.. and let me know if you have any doudt.

package com.blt;

public class ThreadExample implements Runnable {
    public static void main(String args[]) {
        Thread T1 = new Thread(new ThreadExample());
        Thread T2 = new Thread(new ThreadExample());
        try {
            T1.setName("thread 1");
            T1.start();
            T2.setName("thread 2");
            T2.start();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void run() {

        synchronized (ThreadExample.class) {
            for (int i = 0; i < 5; i++) {
                try {
                    ThreadExample.class.notify();
                    System.out.println("Thread going to wait state::"+ Thread.currentThread().getName());
                    ThreadExample.class.wait(400);
                    System.out.println("Thread notified is::"+ Thread.currentThread().getName());
                    System.out.println("Thread going to sleep state::"+ Thread.currentThread().getName());
                    Thread.sleep(2000);
                    System.out.println("==========");

                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }
    }
}