Question

If class a extends class b, and class b extends class c, does a inherit from both c and b? If so, in case of conflict between the 2, is there an error or does one override another (and if so, which one)?

Please rename the question if it is unsuitably titled.

EDIT: what I mean by conflict is something like the following:

class c {
   int foo;
   //Stuff
}
class b extends c {
   String foo;
   //Stuff
}
class a extends b {
   //Stuff
}

Is a.foo a string or an int?

Another edit: So from what I gather, inheritance here is a bit like CSS – the closer the rule is set, the larger priority it has (e.g. inline styles override stylesheets). Is that a good way of considering this, or is it significantly different?

Answer 1

Yes, a inherits from b and c. I don’t see how there can be a conflict in this situation since b’s method overrides will be valid for a. You may be thinking of the diamond problem that comes from conflicts from multiple inheritance, but that’s when you have two different parents, not two parents with one parent being the parent of the other.

You can run into a “soft” diamond problem with interfaces, where two methods have the same signature, but the rules for one method don’t match those of another. Since neither interface has an implementation for their methods, there is no compilation problem (that I know of), just a logical problem.

Edit Ah, I’ve seen your edit regarding variables, and I agree with Jimpanzee’s response to it. It’s certainly easy to test:

public class Test3 {
   public static void main(String[] args) {
      MyA myA = new MyA();
      System.out.println("foo := " + myA.foo);
   }
}

class MyC {
   public int foo = 3;
   //Stuff
}
class MyB extends MyC {
   public String foo = "foo";
   //Stuff
}

class MyA extends MyB {

}