ABSTRACT CLASS IN JAVA

It is a partially implemented class used for developing some of the operations of an object which are common for all next level sub classes. A class that is declared as abstract using abstract modifier is called abstract class. It contains both abstract methods, concrete methods including variables, blocks and constructors. It is always created as super class next to interface in object’s inheritance hierarchy for implementing common operations from interface. A method that is declared as abstract and does not have implementation is known as abstract methods. Abstract class is basically used to have defined and declared methods both. 

Suppose if we have some method to define but currently we don’t have its solution, so simply we can declare that method. And in the future we can define that class by extending it.

Note – We cannot create object of abstract class.

Example –

abstract class Mobile{

          public abstract void call();

          public abstract void playMovie();

          public abstract void hasGame();

          public abstract void hasVideochat();

}

abstract class Samsung extends Mobile{

          @Override

          public void call() {

                   System.out.println("Samsung implemented calling facility");            

          }

          @Override

          public void playMovie() {

                   System.out.println("Samsung implemented movie facility");             

          }

          public abstract void hasGame();

          public abstract void hasVideochat();

}

abstract class Mi extends Samsung{

          public void hasGame()

          {

                   System.out.println("Mi implemented gaming facility");

          }

}

class Apple extends Mi{

          @Override

          public void hasVideochat() {

                   System.out.println("Apple implemented videochat");

          }       

}

class Tesr1 {

          public static void main(String[] args) {

                   Apple a = new Apple();

                   a.call();

                   a.hasGame();

                   a.hasVideochat();

                   a.playMovie();

          }

}

Output –

Samsung implemented calling facility

Mi implemented gaming facility

Apple implemented videochat

Samsung implemented movie facility

Example –

abstract class Mobile{

          public abstract void showConfig();

}

class Mi extends Mobile{

          @Override

          public void showConfig() {

                   System.out.println("3GB Ram, 32GB Memory, 16MP camera");                

          }       

}

class Samsung extends Mobile{

          @Override

          public void showConfig() {

                   System.out.println("2GB Ram, 16GB Memory, 13MP camera");                 

          }       

}

class Tesr1 {

          public static void main(String[] args) {

                   Mi obj = new Mi();

                   Samsung obj1 = new Samsung();

                   show(obj1);

          }

          public static void show(Object obj)

          {

                   ((Mobile) obj).showConfig();

          }

}

Output –

2GB Ram, 16GB Memory, 13MP camera

Note – In the above example we are passing object to access the configuration of a particular phone, as all phone extends class called Mobile. So whatever object we will pass we can see the configuration of that particular phone.