Java OCA OCP Practice Question 1830

Question

What, if anything, is wrong with the following code? 

// Filename: Main.java
class Main implements T1, T2{
   public void m1 (){}
}
interface T1{//from  w ww. ja v a 2s . c  om
   int V = 1;
   void m1 ();
}
interface T2{
   int V = 2;
   void m1 ();
}

Select 1 option

  • A. Main cannot implement them both because it leads to ambiguity.
  • B. There is nothing wrong with the code.
  • C. The code will work fine only if V is removed from one of the interfaces.
  • D. The code will work fine only if m1 () is removed from one of the interfaces.
  • E. None of the above.


Correct Option is  : B

Note

Having ambiguous fields or methods does not cause any problems by itself but referring to such fields/methods in an ambiguous way will cause a compile time error.

So you cannot call : System.out.println (V);

because it will be ambiguous (there are two V definitions).

But the following lines are valid :. 

Main tc = new Main ();
System.out.println ((  ( T1) tc).V);

However, explicit cast is not required for calling the method m1():((T2)tc).m1();

tc.m1 () is also fine because even though m1 () is declared in both the interfaces, the definition to both resolves unambiguously to only one m1 (), which is defined in Main.




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