About Question enthuware.ocajp.i.v7.2.1204 :

[aditya]

HI Admin ,
when i do following it prints B

Code: Select all

public class TestClass{
  public static void main(String args[ ] ){
    Object a, b, c ;
    a = new String("A");
    b = new String("B"); 
    a = b;   //only swipe this code
    c = a;
       System.out.println(""+c);
  }
}

I read your explanation , but can you please tell me why in above case it is printing B .

Also in explanation you have mentioned that "..c starts pointing to the string object .." where this happens compile time or run time.?

Please explain more and clear my doubt.

[admin]

a = b; this assigns the objected pointed to by b (which is "B") to a. So a points to "B" now.
Then you have c = a; this assigns the objected pointed to by a (which is "B" because of above) to c. So c also points to "B" now.
System.out.println(""+c); // this prints B because c is pointing to B as explained above.

All this happens at run time.

[Deleted User 2655]

Why is Object's class toString method not used in this example?

Why does the String's class toString() method overrides Object's?

[admin]

Why is Object's class toString method not used in this example?

You have asked a very fundamental question. And I would strongly suggest you to read about polymorphism in Java from a good book before attempting any further mock exams. You should come back to this question after reading that.

Why does the String's class toString() method overrides Object's?

I am not sure I understand your question. String's class toString() method overrides Object's toString because that is what the programmer (i.e. the one who coded String class) intended to do. Object's toString doesn't do what the String class wants to do.

HTH,
Paul.

[dxie1154]

So in this question c is pointing to a, and once a points to b, c is still sitting there pointing at new String("a") while a switched its reference and now points at new String("b")?

[admin]

That is correct.