Java - Two methods with same name, same argument of different type, but the types are related hierarchically

Question

Let's say I have

Interface A {
   public void doSomething(Object a);
}

Interface B {
   public void doSomething(Foo b);
}

and

Class C implements A, B {

   public void doSomething(Object a) {  print("a"); }
   public void doSomething(Foo b) { print("b"); }

}

I guess calling new C.doSomething(new Foo()); will print "b", even though Foo extends Object.

but what about if I want a common behavior from sub-methods:

Class C implements A, B {

   public void doSomething(Object a) {  print("common behavior from " + a ); }
   public void doSomething(Foo b) { doSomething((Object) b); }
   public void doSomething(Bar c) { doSomething((Object) c);}

}

Will that work when I call doSomething with Foo and Bar or will they end up in an infinite loop because at the end doing ((Object) c) instanceof Bar == true?

How does Java defines which method to call?

You should try it and find out. Java defines the behavior in it's specifications. — castletheperson
– castletheperson, Commented Sep 26, 2016 at 23:25

shmosel · Accepted Answer · 2016-09-26 23:25:44Z

2

Overload resolution happens at compile time. It doesn't matter what the runtime type of b or c is. As long as they're cast as Object, it'll call the Object overload. So your example should work fine.

Another common use case is where you want to pass a literal null to a method and you need to cast it to some type to avoid overload ambiguity. E.g. c.doSomething((Foo)null).

answered Sep 26, 2016 at 23:25

shmosel

51k7 gold badges81 silver badges147 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

htafoya Over a year ago

Using the null parameter is a good example explanation. Thank you.

Collectives™ on Stack Overflow

Java - Two methods with same name, same argument of different type, but the types are related hierarchically

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related