Inheritance made me Mad today

[Sahil Kapoor]

Consider the following program :-

  class WTF {
  public static void main(String... args) {
  }
}

class Animal {
  static void method(){}
  static String name="Animal";
}

class Dog extends Animal {
  //void method(){}; // CTE :  method() in Dog cannot override method() in Animal; overridden method is static, OKAY !!!
  String name="Dog";  // Complier is Okay with this. ??? why ??? and why not with methods ??????
}  

Oooopppssss!!!

[Seetharaman Venkatasamy]

1. you cant override static method, since it is not bound to an Object. but it can be re-defined[in subclass also give static modifier]

2. class attribute can not be inherit in subclass. i.e, super class name reference variable is different from subclass name variable

hth

[Sahil Kapoor]

Seetharaman Venkatasamy wrote:1. you cant override static method, since it is not bound to an Object. but it can be re-defined[in subclass also give static modifier]

2. class attribute can not be inherit in subclass. i.e, super class name reference variable is different from subclass name variable

hth

IMO , they are inherited , consider the following code :-

   class WTF {  
   public static void main(String... args) {  
     System.out.println(Dog.name);
   }  
 }  
   
 class Animal {  
   static void method(){}  
   static String name="Animal";  
 }  
   
 class Dog extends Animal {  
   
 }       

Prints Animal !!! evidence that static members are inherited.

[Yves Caron]

This is not inheritance. A static member belongs to the class where it is defined.

You can use the class name to reference it. You can use an instance of the class to reference it. In the later case, the compiler replaces the instance's name by the class's name.

The compiler knows that Dog extends Animal. If it cannot find a definition in Dog for the static variable "name", it substitutes Dog for Animal. It will go up the hierarchy tree until it finds a definition or concludes that it is not defined.

As Seetharaman mentioned, static members can be redefined. In which case, the compiler finds the definition right away.

If you look carefully, you will see that static variables and static method behave the same way.

class WTF {
    public static void main(String... args) {
        System.out.println(Animal.name);
        System.out.println(Dog.name);
        Animal.method();
        Dog.method();
    }
}

class Animal {
    static void method() { System.out.println("Animal method()"); }
    static String name = "Animal";
}

class Dog extends Animal {
    static void method() { System.out.println("Dog method()"); }
    static String name = "Dog";
}

Here is the output of the code above:
Animal
Dog
Animal method()
Dog method()

Thank you. Take care.

[Abimaran Kugathasan]

Related to Overriding & Overloading,
1) A compilation error occurs if an instance method overrides a static method.
2) A compilation error occurs if a static method hides an instance method.
3) It's possible for a static variable to hide an instance variable.
4) It's also permissible for an instance variable to hide a static variable.

For static methods, the compiler uses the declared type of reference. That's what we mean when we say a static method doesn't have run-time polymorphism, Because instance methods and class methods have this important different in behaviors, we use different terms - "overriding" for instance methods, and "hiding" for class methods.

When we say, you can't override a static method, what that means is even if you write code that looks like it's overriding a static method - it won't behave like an overriden method(no polymorphism)

[Sahil Kapoor]

Thanks Abimaran......Thats what i was asking !!!
I got it now....

But i also observed the same behaviur and wrote as rules.....But do you know the logic behind above rules ???