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

class TrueOrFalse {
    public static void main ( String [] args ) {
        A a = new A ();
        B b = new B ();
        C c = new C ();
        D d = new D ();
        A e = new D ();
        A f = new B ();

        System.out.println("a) " + (b instanceof A)); // true
        System.out.println("b) " + (c instanceof D)); // false
        System.out.println("c) " + (d instanceof A)); // true
        System.out.println("d) " + (e instanceof C)); // true
        System.out.println("e) " + (f instanceof C)); // false

        //Tilfelle 1
        // B ab = (B) a;    //Kræsjer

        //Tilfelle 2
        if ( e instanceof B ){
            B eb = (B) e;
        }

        //Tilfelle 3
        // D ed = (D) e;   //Kræsjer

        //Tilfelle 4
        if ( e instanceof D ){
            D ed = (D) e;
        }

        //Tilfelle 5
        B fb = (B) f;

        //Tilfelle 6
        C ec = (C) e;
    }
}