method hiding a method in super class

[san ch]

Hi

1. Consider the following two classes:
 
public class ClassA {
    public void methodOne(int i) {
    }
    public void methodTwo(int i) {
    }
    public static void methodThree(int i) {
    }
    public static void methodFour(int i) {
    }
}
 
public class ClassB extends ClassA {
    public static void methodOne(int i) {
    }
    public void methodTwo(int i) {
    }
    public void methodThree(int i) {
    }
    public static void methodFour(int i) {
    }
}

a. Which method overrides a method in the superclass?
b. Which method hides a method in the superclass?
c. What do the other methods do?

i could identyfy that the second method will be override the method in the super class

i couldnt understand why method four hides the method four in the super class......

i am thinking, since static methods cant be overridden. any method which is implementd with the same signature in the sub class hides the super class method.

is my thinking right

pls explain

thank you
san

[Steven Bell]

You are pretty much right. The confusion will come in if you try to call one of the static methods from an instance (which is why you should always call from a Class). If you:

ClassA ref = new ClassB();
ref.methodFour(4);

the method in ClassA will be called, but make one little change:

ClassB ref = new ClassB();
ref.methodFour(4);

and the method in ClassB will be called. This is because the method is chosen at compile time based on the type of the reference not the type of the object. You will also get similar behaviour with non-static methods that are overloaded take a different type of parameter such as:

public ClassA{
  public void method(Object o){
  }
}
public ClassB extends ClassA{
  public void method(String s){
  }
}
//somewhere else
ClassA ref = new ClassB();
ref.method("Help"); //calls method in ClassA
ClassB ref2 = (ClassB)ref;
ref2.method("Help"); //calls method in ClassB

I hope I helped more than confused.

[san ch]

Hi steven

Thank you for the explaination it was indeed nice ......one small doubt
are there any other occasions where the super class method will be hidden by the subclass methods ....or is it only when the method is a static method

[Steven Bell]

The method is only hidden when it's static.