overriding

abstract class A { int met(A a) { return 0; } int met(B b) { return 1; } int met(C c) { return 2; } } class B extends A { int met(A a) { return 3; } int met(B b) { return 4; } int met(C c) { return 5; } } class C extends B { int f() { return ((A)this).met((A)this); } } public class teste { public static void main(String args[]) { C x = new C(); System.out.println(x.f()); } } The program will return 3 and I was expecting 0. Why does the first cast in the method f do nothing and the second one works? Is it because in the A and B classes the met methods are overloaded and therefore static binding

I am trying to override a method in the superclass in my java subclass and then call the overriden method from the superclass. Is this the correct way to do it. The method in the super class i want to overrride is called describe() public static void describe() { Item.describe(); } Use the super keyword. @Override public void describe() { super.describe(); } Note the annotation which although is not necessary is "correct". As was pointed out, static methods do not get inherited. It's possible to imitate polymorphic behavior with static methods using reflection but I do not recommend this for a

In the SCJP book by Kathey Sierra, an excerpt is as follows: If a method is overridden but you use a polymorphic (supertype) reference to refer to the subtype object with the overriding method, the compiler assumes you’re calling the supertype version of the method. If the supertype version declares a checked exception, but the overriding subtype method does not, the compiler still thinks you are calling a method that declares an exception (more in Chapter 5). Let’s take a look at an example: class Animal { public void eat() throws Exception { // throws an Exception } } class Dog2 extends

I have this simple piece of code. abstract class X { X() { read(); } private void read() { Object obj = new Object(); readValue(obj); } protected abstract void readValue(Object obj); } class Y extends X { Object obj = null; Y() { super(); } @Override protected void readValue(Object obj) { this.obj = obj; } void printer() { System.out.println("Object = " + obj); } } class Runner { public static void main(String[] args) { Y y = new Y(); y.printer(); } } When I run the above code, the object gets printed as null. (I get "Object = null" ) Surprisingly, in class Y when I remove null declaration

I have an easy 'homework' to do, but I have found a little problem with the closure of the input stream. To put it simply, I have to make a contact 'list' application in Java, just to use the polymorphism in the correct way. So I have a class Contact and a subclass Private (contact). In both class there is a modify method to change the value of the variables. public void modify() throws IOException { System.out.println("Previously name: " + name); System.out.println("Insert new name"); try(InputStreamReader ir = new InputStreamReader(System.in); BufferedReader in = new BufferedReader(ir) ) {