Doubt on Thread- wait()

[Saumya Srivastava]

Hi,

I was running the code below and thought of commenting the line calling notify(). So that I may see if I get IIlegalMonitorStateException. But the code ran successfully without throwing error. Please explain me why? Isn't it necessary for the thread to send notify() to the waiting thread? I think main() thread should throw the exception after not receiving notification from ThreadB b? Please correct me ...if my understanding is wrong..?

    

public class ThrdWaitNotify {
		public static void main(String[] args) {
		ThreadB b=new ThreadB();
		b.setName("B");
		b.start();
		
		synchronized(b){
			try{
				System.out.println("Waiting for b to complete...");
				System.out.println("Current thread is :"+Thread.currentThread().getName());
				b.wait();
			}catch (InterruptedException e) {}
			System.out.println("Total is: " + b.total);
		}
	}

}

class ThreadB extends Thread{
	int total;
	
	public void run(){
		synchronized(this){
			System.out.println("Current object is :"+Thread.currentThread().getName());
			for(int i=0;i<5;i++){
				total+=i;
			}
			System.out.println("notifying..");
//			notify();
		}
	}
}

[Mohit G Gupta]

it's not necessary to call notify

It's simply to notify waiting thread to wake up.
if not implemeted,the waiting thread would not wake up
that's it..