exam lab practice exam -1, question24 need justification?

[Arjun Srivastava]

  
class A{
     synchronized void doTask1(){
          System.out.print(1);
     }

}

class B extends Thread{

     A a; Thread t;

     B(A a, Thread t){
          this.a=a; this.t=t;
     }

     public void run(){
          doTask2();
     }

     public void doTask2(){
          synchronized(a){
               try{
                    t.join();
               }catch(Exception e){}
          }
     }

     public void doTask3(){
          synchronized(a){
               System.out.print(2);
          }
     }

}

public class TDemo{

     public static void main(String args[]) throws Exception{
          A a=new A();
          B b=new B(a,Thread.currentThread());
          b.start();
          Thread.sleep(1000);
          a.doTask1();
          b.doTask3();
     }
}

answer is it prints nothing and program never terminates, yes that is true,it shows.
in this question 24 of practice exam 1
as sleep method throws interrupted exception it must have to be used inside a try and catch clause.
but here it is nothing like that line 43.
???

[Ankit Garg]

Since the main method throws Exception, so the code in it can throw any checked exceptions that are sub-classes of java.lang.Exception class...