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

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 09:31:35