Static methods in interfaces

Question

Java cognoscenti,
Anyone know why I can't declare a method as static in an interface, but I can in an abstract class. Surely, semantically it's the same - defering the implementation of a static method, not an abstract class and an interface. By the way, I'm using JDK 1.2.2 if that makes a difference

Answer 1

No, it's not the same. You are not "defering the
implementation of a static method" because static
methods are never polymorphic.
Static methods cannot be abstract for this reason, and
only abstract methods are allowed in interfaces.I didnt't know that. I thought that - because you can override static methods and you can call them onto an actual instance the method binding would be done at run-time, not at compile-time. So I was trying to prove you wrong, but you are correct !
A short summary of what I've learnt so far:
- interfaces cannot contain static methods
- abstract classes cannot contain abstract static methods
- static methods can be overriden, but they are not polymorphic; this means that the compiler decides which method to call at compile-time.
/* output
SuperClass.someMethod()
SubClass.someMethod()
SuperClass.someMethod()
SuperClass.someMethod()
SubClass.someMethod()
SubClass.someMethod()
SuperClass.someMethod()
public class Test {
  public final static void main(String[] args) {
      // output: SuperClass.someMethod()
      new SuperClass().someMethod();
      // output: SubClass.someMethod()
      new SubClass().someMethod();
      // output: 2x SuperClass.someMethod()
      SuperClass someClass1 = new SubClass();
      someClass1.someMethod();
      showSuper(someClass1);
      // output: 2x SubClass.someMethod()
      SubClass someClass2 = new SubClass();
      someClass2.someMethod();
      showSub(someClass2);
      showSuper(someClass2); // SuperClass.someMethod()
  public final static void showSuper(SuperClass c) {
        c.someMethod();
  public final static void showSub(SubClass c) {
        c.someMethod();
class SuperClass {
  public static void someMethod() {
    System.out.println("SuperClass.someMethod()");
class SubClass extends SuperClass {
  public static void someMethod() {
    System.out.println("SubClass.someMethod()");