Method Overriding in Java

Method Overriding in Java

If subclass (child class) has the same method as declared in the parent class, it is known as method
overriding.In other words, If subclass provides the specific implementation of the method that has been provided by one of its parent class, it is known as Method Overriding.

Advantage of Java Method Overriding

1. Method Overriding is used to provide specific implementation of a method that is already provided by its super class.

2. Method Overriding is used for Runtime Polymorphism.

Rules for Method Overriding

    1. method must have same name as in the parent class
    2. method must have same parameter as in the parent class.
    3. must be IS-A relationship (inheritance).

Understanding the problem without method overriding

Let's understand the problem that we may face in the program if we don't use method overriding.

      class Vehicle{ 
      void run(){System.out.println("Vehicle is running");} 
      } 
      class Bike extends Vehicle{ 
       
      public static void main(String args[]){ 
      Bike obj = new Bike(); 
      obj.run(); 
      } 
    } 

Output:Vehicle is running

Problem is that I have to provide a specific implementation of run() method in subclass that is why we use method overriding.

Example of method overriding

In this example, we have defined the run method in the subclass as defined in the parent class but it has some specific implementation. The name and parameter of the method is same and there is IS-A relationship
between the classes, so there is method overriding.

    class Vehicle{ 
    void run(){System.out.println("Vehicle is running");} 
    } 
    class Bike extends Vehicle{ 
    void run(){System.out.println("Bike is running safely");} 
     
    public static void main(String args[]){ 
    Bike obj = new Bike(); 
    obj.run(); 
    } 

Output:Bike is running safely


Real example of Java Method Overriding

Consider a scenario, Bank is a class that provides functionality to get rate of interest. But, rate of interest
varies according to banks. For example, SBI, ICICI and AXIS banks could provide 8%, 7% and
9% rate of interest.

 

class Bank{ 
    int getRateOfInterest(){return 0;} 
    } 
     
    class SBI extends Bank{ 
    int getRateOfInterest(){return 8;} 
    } 
     
    class ICICI extends Bank{ 
    int getRateOfInterest(){return 7;} 
    } 
    class AXIS extends Bank{ 
    int getRateOfInterest(){return 9;} 
    } 
     
    class Test{ 
    public static void main(String args[]){ 
    SBI s=new SBI(); 
    ICICI i=new ICICI(); 
    AXIS a=new AXIS(); 
    System.out.println("SBI Rate of Interest: "+s.getRateOfInterest()); 
    System.out.println("ICICI Rate of Interest: "+i.getRateOfInterest()); 
    System.out.println("AXIS Rate of Interest: "+a.getRateOfInterest()); 
    } 
    } 

Output:
SBI Rate of Interest: 8
ICICI Rate of Interest: 7
AXIS Rate of Interest: 9

 

Can we override static method?

No, static method cannot be overridden. It can be proved by runtime polymorphism so we will learn
it later.

Why we cannot override static method?

because static method is bound with class whereas instance method is bound with object. Static belongs

to class area and instance belongs to heap area.

Can we override java main method?

No, because main is a static method.

What is the difference between method Overloading and Method Overriding?

There are three basic differences between the method overloading and method overriding.
They are as follows: 

               Method Overloading                                               Method Overriding

1) Method overloading is used to                           Method overriding is used to provide the specific

    increase the readability of the program.               implementation of the method that is already

                                                                              provided by its super class.

2) Method overloading is performed                      Method overriding occurs in two classes that have IS-A
    within a class.                                                    relationship.      

3) In case of method overloading                           In case of method overriding parameter must be same.
   parameter must be different.

More topics on Method Overriding (Not For Fresher)

Method Overriding with Access Modifier
Let's see the concept of method overriding with access modifier.

Exception Handling with Method Overriding
Let's see the concept of method overriding with exception handling.