Final keyword in method signatures [duplicate]

Question

Possible Duplicate:
Final arguments in interface methods - what’s the point?

While trying to experiment a few things, I've ran into a problem that it's described in this page.

interface B {
    public int something(final int a);
}

abstract class C {
    public int other(final int b);
}

class A extends C implements B {

    public int something(int a) {
        return a++;
    }

    public int other(int b) {
        return b++
    }
}

Why is such feature possible? I don't know why it's possible to to make a final parameter into a non-final one by just overriding the method. Why is the final keyword ignored in a method signature? And how do I obligate sub-classes to use in their methods final variables?

Answer 1

Java passes arguments to a method by value.

Therefore, no changes to a parameter can propagate back to the caller. It follows that whether or not the parameter is declared final makes absolutely no difference to the caller. As such, it is part of the implementation of the method rather than part of its interface.

What's your motivation for wanting to "obligate sub-classes to use in their methods final variables"?