Java Method Overriding

Method Overriding means declaration of same method in the subclass which is already present in the Base class in the inheritance.

In Method Overriding child class can give it's own implementation of the method of Parent class.

Method Overriding

When an overridden method is called then, the method defined by the subclass is executed and method defined by the superclass is hidden.
Superclass methods are inherited by it's subclass and its used by the objects of subclass also.

Syntax

class class1
{
  type method1()
  {
     ...
     ...
  }
}

class class2 extends class1
{
   type method1()
   {
      ...
      ...
   }
}

In above syntax the method1 is redefined in the subclass

Example of Method Overriding

class Phone
{
    String os,ram,company;
    String model,camera;
    int battery;
    Phone()	//constructor for initialization
    {
	model = "Galaxy S9";
	camera = "12 Mega Pixel";
	os = "Android 8.0";
	battery = 3000;
    }
    void display()	// method defined
    {
	System.out.println("Phone Detailes are \n");
	System.out.println("Model Name : "+model);
	System.out.println("Camera : "+camera);
	System.out.println("Batter power : "+battery+" mAh");
    }
}

class Computer extends Phone
{
    Computer()
    {
	os = "Windows 10";
	ram = "8 GB";
	company = "Asus";
    }
    void display()	// method defined again
    {
	super.display();	// for executing superclass display method
		
	System.out.println("Computer Detailes are \n");
	System.out.println("Company : "+company);
	System.out.println("Operating System : "+os);
	System.out.println("RAM Capacity : "+ram);
    }
}
class Hardware
{
    public static void main(String args[])
    {
	Computer myComputer = new Computer();
	myComputer.display();	// executes subclass display method only
    }
}

Output

Phone Detailes are

Model Name : Galaxy S9
Camera : 12 Mega Pixel
Batter power : 3000 mAh

Computer Detailes are

Company : Asus
Operating System : Windows 10
RAM Capacity : 8 GB

Explanation

  • In class Phone we have defined the display() for showing the phone details.
  • In class Computer again we have defined same method display() for showing Computer details
  • We have created the object of Child class and called the display() method. It will only execute the display method of class Computer instead of class Phone, because the object created is a child class.
  • To execute Parent's display method we need to call it by using super keyword
  • This concept is called as the runtime Polymorphism.

Difference between Method Overloading and Method Overriding

Overloading and Overriding is a kind of polymorphism. Which means "having one name" and "many forms".
Following difference clearly specifies the difference between method overloading and method overridden concept

Parameter Method Overloading Method Overriding
Definition In method Overloading, methods of the same class shares the same name but must have different number of parameters or parameters in different order. In method Overriding, superclass and subclass have the same method name,same type and same number of parameters.
Meaning It means more than one method having same name but different type of parameters It means base class method is redefined in the derived class having same type,method name and parameters list.
Polymorphism Method Overloading is a Compile time polymorphism Method Overriding is a Run Time polymorphism
Inheritance It may or may not needed the inheritance to implement Method Overloading. It always requires inheritance to implement Method Overriding.
No of classes In this doesn't require more than one class for overloading. In this it requires at least two classes to implement overriding
Example 
class first
{
  int add(int a, int b)
  {	
     return a+b;
  }
  float add(float a, float b)
  {
   	 return a+b;
  }
}	

class first
{
   int add(int a, int b)
   {
      return a+b;
   }
}
class second extends first
{
   int add(int a, int b)
   {
      return a+b;
   }
}
<< Previous Next >>