QUESTION 14

QUESTION 14 
Given: 
 
1. class One { 
2.     public One foo() { 
3.         return this; 
4.     } 
5. } 
6.  
7. class Two extends One { 
8.     public One foo() { 
9.         return this; 
10.     } 
11. } 
12. 
13. class Three extends Two { 
14.     // insert method here 
15. } 
 
Which two methods, inserted individually, correctly complete the Three class? (Choose two.) 
 
A. public void foo() {} 
B. public int foo() { return 3; } 
C. public Two foo() { return this; } 
D. public One foo() { return this; } 
E. public Object foo() { return this; } 
Solution : CD 
 

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plus imformation 

A. Main.java:14: foo() in Three cannot override foo() in Two;

   attempting to use incompatible return type 

   found   : void

   required: One     

   public void foo() {}

                 ^ 1 error 

 

B. Main.java:14: foo() in Three cannot override foo() in Two;

   attempting to use incompatible return type 

   found   : int 

   required: One

   public int foo() { return 3; }

             ^ 1 error 

 E. Main.java:14: foo() in Three cannot override foo() in Two;

    attempting to use incompatible return type

    found   : java.lang.Object 

    required: One

    public Object foo() { return this; }

                 ^ 1 error