QUESTION 60

QUESTION 60 
Given: 
 
1. public interface A { public void m1(); } 
2.  
3. class B implements A { } 
4. class C implements A { public void m1() { } } 
5. class D implements A { public void m1(int x) { } } 
6. abstract class E implements A { } 
7. abstract class F implements A { public void m1() { } } 
8. abstract class G implements A { public void m1(int x) { } }  
 
What is the result? 
 
A. Compilation succeeds. 
B. Exactly one class does NOT compile. 
C. Exactly two classes do NOT compile. 
D. Exactly four classes do NOT compile. 
E. Exactly three classes do NOT compile. 
Solution : C
 

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plus imformation 

Main.java:3: 

B is not abstract and does not override abstract method m1() in A class B implements A { } 

^ 

Main.java:5: 

D is not abstract and does not override abstract method m1() in A class D implements A { public void m1(int x) { } } 

^ 2 errors

class 에서 interface사용시 그대로 사용 .

abstract class 에서 interface 사용시 변경 사용 가능 (선언)