Java : Overriding and Overloading Concepts and Difference.

Hello friends, I know overloading/overriding are one of the famous OOB concepts that everyone knows JBut I feel more often people got confuse in this concepts.

Please go through the below diagram that will give you broad picture and lets understand point by point.

Overriding:

• Overriding is runtime polymorphism
• Happens in different class and Use in Inheritance : Overriding is concept that use in Inheritance where super class and sub class has same method name and same arguments

           Ex.

class Animal {

     public void myOverRiding ()

     {

      System.out.println("This is animal overriding ");

     }

}

class Horse extends Animal {

     public void myOverRiding ()

     {

      System.out.println("This is horse overriding ");

     }

}

• Can we prevent overriding?

o   “Final” keyword can be prevent class to be inherited that means technically we are preventing overriding.

o   It will throw following compile time error.

•  JVM decides what to do at run time: when you are calling any method with help of sub/super class object, JVM decides at run time that method of which class needs to be called

      public class UserAnimal {

     public static void main(String s[])

     {

           Animal aniHr =  new Horse(); //Line 4

           aniHr.myOverRiding();

   //In overriding it will call actual object class method.

     }

}

class Animal {

     public void myOverRiding ()

     {

           System.out.println("This is animal overriding ");

     }

}

class Horse extends Animal {

    

public void myOverRiding ()

     {

          System.out.println("This is horse overriding ");

     }

}

                                In above example we have two classes Animal – Super class and Horse – Sub class which shares same method called myOverRiding() now in UserAnimal class we have created an object of Horse and reference of Animal (refer Line # 4) and we called myOverRiding() method with help of that object (aniHr) now question is, which class’s method myOverRiding() will be called ? Any guess?

     Answer, in overriding JVM runtime use actual object and in overloading JVM use reference (Animal) instead of actual object (Horse)

O/P:  This is horse overriding

Overloading:

• Overloading is compile time polymorphism
• Happens in same class only
• Method can have same name and different arguments

   class Animal { 

   MyStuff() {  System.out.println("Hi Cow");  }

   MyStuff(int i) { System.out.println("Hi Dog");  }

  }

• Can we prevent override? Unlike override prevent with final keyword with class , java don’t have anything to prevent overload in class (unless you wish to not write same method name J )
• JVM decides everything at compile time : which class method needs to be called that will decide at compile time (in overloading JVM use reference (Animal) instead of actual object (Horse))
• If you try to write same method with same arguments it will throw compile time error.

Ex.  This is the similar example which I have explained above just o/p is different

public class UserAnimal {

     public void doStuff(Animal a)

     {

           System.out.println("This is animal ");

     }

     public void doStuff(Horse a)

     {

           System.out.println("This is horse");

     }

     public static void main(String s[])

     {

           UserAnimal obj = new UserAnimal();

           Animal aniHr =  new Horse();

           obj.doStuff(aniHr)

       //In overloading it will call reference class method.

     }

}

class Animal {

}

class Horse extends Animal {

}

O/P: This is animal

Hope this article would be value added and helpful, have a happy learning J

Thanks,

Sagar Vyas