What is the difference between abstract class and a concrete class in Java?

Java 8 Object Oriented Programming Programming

Following are the notable differences between an abstract class and concrete class.

Abstract class

Abstract classes may or may not contain abstract methods, i.e., methods without body ( public void get(); )
But, if a class has at least one abstract method, then the class must be declared abstract.
You cannot instantiate an abstract class.
An abstract class may contain abstract methods.
You need to inherit an abstract class to use it.
If you inherit an abstract class, you have to provide implementations to all the abstract methods in it.

Example

public abstract class AbstractExample {
   public abstract int add(int a, int b);
   public abstract int subtract();
   
   public void display(){
      System.out.println("Hello how are you");
   }
}

Concreate class

You can instantiate a concrete class.
A concrete class doesn’t have any abstract methods.
It is not mandatory to inherit a concrete class to use it.

Example

Live Demo

public class ConcreteClassExample {
   public int add(int a, int b){
      int c = a + b;
      return c;
   }
   public int subtract(int a, int b){
      int c = a - b;
      return c;
   }
   public void display(){
      System.out.println("Hi welcome to Tutorialspoint");
   }
   public static void main(String args[]){
      ConcreteClassExample obj = new ConcreteClassExample();
      System.out.println(obj.add(25, 347));
      System.out.println(obj.subtract(500, 456));
      
      obj.display();
   }
}

Output

372
44
Hi welcome to Tutorialspoint

Sai Subramanyam

Published on 29-Dec-2017 05:01:35

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