There are two interfaces B and C each having the same method public m1()
class A implements B and C If class A has to implement method m1(), the implemented method would be of which interface?
- You will receive an ambiguity error, I believe. :)Konstantin Yovkov– Konstantin Yovkov2013-11-18 10:17:29 +00:00Commented Nov 18, 2013 at 10:17
- try out with simple program and check with the output. It seems to be interview question.Hariharan– Hariharan2013-11-18 10:18:44 +00:00Commented Nov 18, 2013 at 10:18
- See stackoverflow.com/questions/2598009/…ice-phoenix– ice-phoenix2013-11-18 10:19:31 +00:00Commented Nov 18, 2013 at 10:19
- Actually that's a good question. +1.Maroun– Maroun2013-11-18 10:20:07 +00:00Commented Nov 18, 2013 at 10:20
- 1I had asked similar question but it was interface and abstract class stackoverflow.com/questions/11296789/…Nandkumar Tekale– Nandkumar Tekale2013-11-18 10:22:55 +00:00Commented Nov 18, 2013 at 10:22
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6 Answers
I think we can say that A.m1 implements both B.m1 and C.m1. Because both
B b = new A(); b.m1(); and
C c = new A(); c.m1(); will work
answered Nov 18, 2013 at 10:20
Evgeniy Dorofeev
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This is a common problem, this is why having clear instructional method names is important. And good OOP design that will make same methods be abstract.
It is also the reason things are separated out in to classes.
Animal.eat() Fish extends Animal Fish.eat() Dog extends Animal Dog.eat() 
2 Comments
arne.b
How does that deal with the question of one method defined in two interfaces?
Peter_James
@arne.b It shows that in good designs and throughout design structure, this cross of method names will be minimized. A common example is
getSauce(...) and setSauce(...) without the get/set it would just be sauce(...) which could mean either, or or both.Interface have does not have method body,So it hardly matters which method is implemented
See the following example
package test; public class a implements i,j{ @Override public void run() { // TODO Auto-generated method stub } } package test; public interface i { public void run(); } package test; public interface j { public void run(); } In the class a run() is overridden but does it matter if it is from interface i or j
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Since interfaces do not have the implementation, it doesn't matter. There are no deadly diamond of death sort of issues here.
answered Nov 18, 2013 at 10:22
Muhammad Kashif Nazar
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There will be no problem as long as declarations of m1 in B and C are "compatible", i.e. have the same return value.
E.g.
public interface B { void doit(); } public interface C { void doit(); } public class A implements B, C { @Override public void doit() { // TODO Auto-generated method stub } } but if the return type differ then it's not clear which is to be called and that will result in compile error like "The return type is incompatible with B.doit()"
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You have to add only one public m1() method. It will be for both the intefaces. And if both the interfaces have the same parameters,the method declaration will be public m1().
