Differences Between Abstract Class and Concrete Class in Java

Abstract class and concrete class are fundamental concepts of object oriented programming in Java. In this article, we will learn the differences between an abstract class and concrete class.

What is an Abstract Class?

An abstract class is a class that cannot be used to create objects. It can only be accessed using its subclasses. It can contain abstract methods, which are methods without a body. It acts as a blueprint for its subclasses. It can also contain concrete or regular methods.

Example

This example shows how to implement an abstract class in java:

public class JavaTester {
   public static void main(String args[]) {
      Cat lion = new Lion();
      lion.eat();
   }
}
// Cat class is an abstract class
abstract class Cat {
   abstract public void eat();
}
//Lion class is a concrete class which inherits the Cat class.
class Lion extends Cat {
   public void eat() {
      System.out.println("Lion eats");
   }
}

Output

The above program produces the following result :

Lion eats

What is a Concrete Class?

A concrete class in Java is a complete class that has fully implemented methods. A concrete class can be instantiated, which means we can create objects of a concrete class directly using the new keyword. It does not contain any abstract methods.

Example

The following example shows how to implement a concrete class in Java:

public class Cat {
   void meow() {
      System.out.println("Cat meows");
   }

   public static void main(String[] args) {
      Cat myCat = new Cat();
      myCat.meow();
   }
}

Output

The above program produces the following output:

Cat meows

Abstract Class vs Concrete Class

The following table summarizes the differences between abstract and concrete classes: