QUESTION 3

QUESTION 3 

Given: 

class ClassA {} 

class ClassB extends ClassA {} 

class ClassC extends ClassA {} 

and: 

ClassA p0 = new ClassA(); 

ClassB p1 = new ClassB();

ClassC p2 = new ClassC(); 

ClassA p3 = new ClassB(); 

ClassA p4 = new ClassC(); 

 

Which three are valid? (Choose three.) 

 

A. p0 = p1; 

B. p1 = p2; 

C. p2 = p4; 

D. p2 = (ClassC)p1; 

E. p1 = (ClassB)p3; 

F. p2 = (ClassC)p4;

Solution : AEF

plus imformation : 

B. 

incompatible types 

found  : ClassC 

required: ClassB 

p1 = p2;      

^ 

 

C. incompatible types 

found   : ClassA 

required: ClassC 

p2 = p4;

      ^ 

 

D. inconvertible types 

found   : ClassB 

required: ClassC 

p2 = (ClassC)p1;

              ^