static method overriding static method

[Dan Culache]

An answer in the study guide by Heller and Roberts says that "static methods cannot override static methods" but the following code works just fine. Any thoughts?

public class Class4  {
  public Class4() {
      H h = new H(); h.m();
      G g = new G(); g.m();
  }
  public static void main(String[] args) {
    Class4 class4 = new Class4();
  }
}
  class H {
    public static void m() { System.out.println(" m() in class H"); } 
  }
  class G extends H {  
    public static void m() { System.out.println(" m() in class G"); }
  }
  

[Barry Gaunt]

Have you tried:

H h = new G();
h.m();

?

[Pallavi Chakraborty]

Hi Dan, Barry,
I tried compiling with
H h = new G();
h.m();
It is giving an error saying h is already defined in Class4.
But I did find something in API documentation.
http://java.sun.com/docs/books/tutorial/java/javaOO/override.html
It says :
Also, a subclass cannot override methods that are declared static in the superclass. In other words, a subclass cannot override a class method.
A subclass can hide a static method in the superclass by declaring a static method in the subclass with the same signature as the static method in the superclass
What does it mean when they say hiding a static method with the same signature.
Pallavi

[Thomas Paul]

Static methods do not participate in polymorphism therefore they are hidden not overridden.
This is one place where C# has Java beat. In C# you can't run static methods (which are class methods) with an object reference.
Think about how we normally execute static methods. We don't do:
H h = new H();
h.m();
we do:
H.m();
Try this: the method that gets executed is determined at compile time for static methods. So when you do something like:
H h = new G();
h.m();
Since h is a pointer to an H object, it is the static method of the H class that will be executed, not the static method of the G class. That is because at compile time the compiler has no idea that h is pointing to a G object.
Static methods don't participate in polymorphism therefore they can't be overridden. They can only be hidden.

[Dan Culache]

Good point, thank you all.
I guess Thomas is right, if you couldn't call a static method using an object reference this would not be confusing.