Overriding in java.txt

Overriding in Java
In any object-oriented programming language, Overriding is a feature that allows a subclass or child class to provide a specific implementation of a method that is already provided by one of its super-classes or parent classes. When a method in a subclass has the same name, same parameters or signature and same return type(or sub-type) as a method in its super-class, then the method in the subclass is said to override the method in the super-class.

Rules for method overriding:

1.Overriding and Access-Modifiers : The access modifier for an overriding method can allow more, but not less, access than the overridden method. For example, a protected instance method in the super-class can be made public, but not private, in the subclass. Doing so, will generate compile-time error.

2.Final methods can not be overridden : If we don’t want a method to be overridden, we declare it as final. Please see Using final with Inheritance .

3.Static methods can not be overridden(Method Overriding vs Method Hiding) : When you defines a static method with same signature as a static method in base class, it is known as method hiding.
The following table summarizes what happens when you define a method with the same signature as a method in a super-class.

A  simple example for overriding:
// Base Class 
class Parent { 
    void show() 
    { 
        System.out.println("Parent's show()"); 
    } 
} 
  
// Inherited class 
class Child extends Parent { 
    // This method overrides show() of Parent 
    @Override
    void show() 
    { 
        System.out.println("Child's show()"); 
    } 
} 
  
// Driver class 
class Main { 
    public static void main(String[] args) 
    { 
        // If a Parent type reference refers 
        // to a Parent object, then Parent's 
        // show is called 
        Parent obj1 = new Parent(); 
        obj1.show(); 
  
        // If a Parent type reference refers 
        // to a Child object Child's show() 
        // is called. This is called RUN TIME 
        // POLYMORPHISM. 
        Parent obj2 = new Child(); 
        obj2.show(); 
    } 
}