ABCD

  Assume the following classes have been defined:

        public class A extends B {
            public String toString() {
        	return "a";
            }
        }

        public class B extends D {
            public void method1() {
        	System.out.println("b 1");
            }
        
            public void method2() {
        	System.out.println("b 2");
            }
        }

        public class C extends D {
            public void method1() {
        	System.out.println("c 1");
            }
        }

        public class D {
            public String toString() {
        	return "d";
            }
        
            public void method1() {
        	System.out.println("d 1");
            }
        
            public void method2() {
        	System.out.println("d 2");
            }
        }

   Consider the following code fragment:

        D[] elements = {new B(), new A(), new D(), new C()};
	for (int i = 0; i < elements.length; i++) {
	    System.out.println(elements[i]);
	    elements[i].method1();
	    elements[i].method2();
	    System.out.println();
	}

   What output is produced by this code?