Java OCA OCP Practice Question 1509

Question

Consider the following classes : 

class MyClass {  
   public void mMyClass (){  }; 
} 

class MyClass2 extends MyClass  {  
   public void mMyClass (){  } 
   public void mMyClass2 ()  {  } 
} 

class MyClass3 extends MyClass2  {  
   public void mMyClass3 (){  } 
}

and the following declarations: 

MyClass x = new MyClass2 (); MyClass2 y = new MyClass2 (); MyClass2 z = new MyClass3 ();

Which of the following calls are polymorphic calls?

Select 3 options 

A. x.mMyClass(); 
B. x.mMyClass2(); 
C. y.mMyClass(); 
D. z.mMyClass3(); 
E. z.mMyClass2(); 
 



Correct Options are  : A C E

Note

A Polymorphic call means the method of the actual class of the object referred by the variable is invoked.

In java, all non-private method calls are polymorphic.

x.mMyClass2() is invalid call.

It will not even compile because the class of x is MyClass, which does not contain method mMyClass2().

Even though the object referred to by x is of class MyClass2 which does contain mMyClass2().

z.mMyClass3() is invalid for the same reason.




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