class A {}
class B extends A {}
class C extends A {}

class Hovedprogram {
    public static void main(String[] args) {
        A a = new A();
        B b = new B();
        C c = new C();
        A d = null;

        System.out.println("a er A: " + (a instanceof A));
        System.out.println("b er B: " + (b instanceof B));
        System.out.println("c er C: " + (c instanceof C));
        System.out.println();

        System.out.println("a er B: " + (a instanceof B));
        System.out.println("a er C: " + (a instanceof C));
        System.out.println();

        System.out.println("b er A: " + (b instanceof A));
        System.out.println("c er A: " + (c instanceof A));
        
        System.out.println("\nnull:");
        System.out.println("d er A: " + (d instanceof A));
        System.out.println("d er B: " + (d instanceof B));
        System.out.println("d er C: " + (d instanceof C));

        // Feil bruk:
        // System.out.println("b er C: " + (b instanceof C));
        // System.out.println("c er B: " + (c instanceof B));

        // // Riktig bruk med casting:
        System.out.println("\nCasting:");
        System.out.println("b er C: " + ((A) b instanceof C));
        System.out.println("c er B: " + ((A) c instanceof B));
        System.out.println("b er B: " + ((A) b instanceof B));
        System.out.println("c er C: " + ((A) c instanceof C));
        System.out.println("a er A: " + ((A) a instanceof A));

        System.out.println("\nObject:");
        System.out.println("a er Object: " + (a instanceof Object));
        System.out.println("b er Object: " + (b instanceof Object));
        System.out.println("c er Object: " + (c instanceof Object));
        System.out.println("d er Object: " + (d instanceof Object));
    }
}