Question

class a extends b {
    void h() {
        System.out.println("class a");
    }
    public static void main(String[]args) {
        b x = new a();
        c y = new b();
        c z = new a();

        x.h();      //output class a
        y.h();      //output class b
        z.h();      //output class a
    }
}

class b extends c {
    void h() {
        System.out.println("class b");
    }
}
class c {
    void h() {
        System.out.println("class c");
    }
}

Whats is the precedence in which it checks which method to call. I am confused as to how the JVM decides which method to call when I use dynamic dispatch. The output in this case is

class a
class b
class a

and when I remove the overridden method from class a the output is

class b
class b
class b

Answer 1

The class used depends on the instantiated type. So if you have an instance of class a (via new a()), then whether the declared variable is of type a, b, or c does not matter for the purpose of which definition of h() is invoked (it will always invoke a.h()).

However, where the declared type does matter is in when choosing an overloaded method. If you have a subclass that overloads an overridden method, then when invoking from a variable declared as the parent class, you will never use the overloaded method. If using a variable declared as being of the subclass, then it will use the overloaded method as appropriate.