3.6. Overriding

Java: all methods are virtual (overridable) by default, final prevents overriding

public class Super {
    public int myMethod(int x, int y) { }
    public final void anotherMethod() { }
}

public class Sub extends Super {
    @Override
    public int myMethod(int x, int y) {
        super.myMethod(x, y);
        // ...
    }
}

Vala: all methods are non-virtual (not overridable) by default, overriding must be explicitly allowed with virtual. So it's the other way round. Vala has override keyword instead of @Override annotation, and it's not optional

public class Super : Object {
    public virtual int my_method (int x, int y) { }
    public void another_method () { }
}

public class Sub : Super {
    public override int my_method (int x, int y) {
        base.my_method (x, y);
        // ...
    }
}