Question regarding covariant returns

[Ken Teoh]

class First {
public Object method1() {
return new String("Based");
}
}

class Second extends First {
public String method1() {
return new String("Derived");
}
}

public class covariant {
public static void main(String[] args) {
First o = new Second();
String s = (String) o.method1();
System.out.println(s);
}
}

For the above code, why does it print Derived instead of Based?
The reference variable of o is First and method1 should be called in First instead of Second

Thanks

[Keith Lynn]

The answer really doesn't have anything to do with the return types. When an instance method is called on an object whose runtime type is the subclass, it doesn't matter what the reference type is, the overidden method is called.

[Ilja Preuss]

As Keith said, it's polymorphism at work. It has nothing at all to do with covariant return types.