Method Overriding in Java

• 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.
• Method overriding is one of the way by which java achieve Run Time Polymorphism.

Usage of Java Method Overriding

• Method overriding is used to provide the specific implementation of a method which is already provided by its superclass.
• Method overriding is used for runtime polymorphism.

Rules for Java Method Overriding

• The method must have the same name as in the parent class.
• The method must have the same parameter as in the parent class.
• There must be an IS-A relationship (inheritance).

What Cannot Be Overridden?

• Static Methods: You cannot override static methods; defining a same-named static method in a subclass is called "method hiding".

• Final Methods: Methods declared with the final keyword cannot be overridden.

• Private Methods: Since private methods are not inherited, they cannot be overridden.

• Constructors: Constructors are unique to their own class and cannot be overridden.
  

class Animal {
   protected void displayInfo() {
      System.out.println("I am an animal.");
   }
}

class Dog extends Animal {
   public void displayInfo() {
      System.out.println("I am a dog.");
   }
}

class Main {
   public static void main(String[] args) {
      Dog d1 = new Dog();
      d1.displayInfo();
   }
}