upcasting confusion while checking instanceof

Question

class Animal
{

}

    class Dog extends Animal
    {

    }

    class main
    {
      public static void main(String args[])
    Animal g= new Dog();
    System.out.println(g instanceof Dog);      // 1st case

    System.out.println(g instanceof Animal);   // 2nd case

}

QUESTION: why the output is true in both cases ?

Answer 1

Because the object that is referenced, at run-time, by local variable g is of type Dog (and thus also an Animal, because Dog extends Animal, though that's missing from your example).

Answer 2

This is polymorphism in action. See here and here.

If you want to avoid this behaviour, use getClass() instead of instanceof. See my answer here for an example.