Thread question from K&B book

[a alph]

Hi,

The question is which letters will eventually appear somewhere in the output?

public class TwoThreads {
     static Thread laurel, hardy;
     public static void main (String []args)  {

         laurel = new Thread() {
         public void run()  {
             System.out.println("A");
                 try{
                     hardy.sleep(1000);
                 }catch (Exception e) {
                     System.out.println("B");
                 }
                 System.out.println("C");
         }

   };

         hardy = new Thread()  {
         public void run()  {
             System.out.println("D");
                 try{
                     laurel.wait();
                 }catch (Exception e) {
                       System.out.println("E");
                 }
                 System.out.println("F");
          }

     };

  laurel.start();
  hardy.start();

}

}

The answer is A, C, D, E, F.

I don't understand why E is in the output?
In the explanation it says, hardy has not synchronized on laurel. So I tried synchronized (laurel) in the code, then it prints A, C, D, F.
But I couldn't understand the concept here?
Please help.

Thanks.

[Siva Masilamani]

You know when you are calling wait method it should be under the synchronized context.

That is the thread should own the lock on the object on which wait method is called.

Due to above reason it throws IllegalMonitorStateException which will be caught by the Exception block and hence prints the Letter E.

[a alph]

Thanks Siva.
I understand now clearly.

[Atwal Usha]

Siva has already explained it very well. The only thing to remember is that wait method should always be called from within the synchronized context.