Question

I’ve got a question about return types in inherited methods in Java. I’ve got a class and an inherited class. In the inherited class, there’s a specific method. It also inherits a method from the parent class that returns instance of itself.

I want something like this class hierarchy:

public class Foo {
    public Foo bar()
    {
        return this;
    }
}

public class FooInherited extends Foo {
    public Whatever baz()
    {
        return new Whatever();
    }
}

My question is if I can call the inherited method from its instance and then call the specific method without overriding the method to return the inherited class or casting the classes explicitly.

Now I want to have a code fragment like this :

FooInherited foo = new FooInherited();
Whatever w = foo.bar().baz();

I feel a difficulty in this, but I’m not very sure if Java has any time saving mechanism for programmers in such situations.

Answer 1

Unless you override the method in the subclass you will have to cast:

FooInherited foo = new FooInherited();
Whatever w = ((FooInherited)foo.bar()).baz();

However, due to covariant return types in java you can override it like this:

public class FooInherited extends Foo {


        @Override
        public FooInherited bar()
        {
            return this;
        }
 ...
 }

After overriding you no longer have to cast because the static type of foo is FooInherited:

FooInherited foo = new FooInherited();
Whatever w = foo.bar().baz();