What is the Difference Between abstract Class and final Class in Java

The main difference between abstract class and final class in Java is that abstract class is a class with abstract and non-abstract methods and allows accomplishing abstraction, while final class is a class that restricts the other classes from accessing its data and methods.

Object-Oriented Programming is widely used in many software projects. It helps to develop a program using a set of objects, and these objects interact with other objects by passing messages. Furthermore, a class is essential to create objects. It is a blueprint to create objects. Moreover, there are various programming concepts in OOP. Two of them are abstract class and final class.

Areas Covered

1. What is an abstract class in Java
      -Definition, Functionality
2. What is the final Class in Java
     -Definition, Functionality
3. Difference Between abstract Class and final Class in Java
     -Comparison of key differences

Key Terms

Class, abstract Class, final Class, Java, Objects, OOP

What is abstract Class in Java

Abstraction is a major paradigm in OOP. It is the methodology of hiding the internal details and displaying only the functionality to the user. It also helps to reduce the complexity of the program. One way of achieving abstraction is by using abstract classes.

A class declared with the abstract keyword is an abstract class. It can consist of abstract methods as well as non-abstract methods. A class can extend an abstract class and provide the implementations for the abstract methods of the abstract class. Even though we cannot create objects using the abstract class, we can create objects from a class that extend the abstract class. An example is as follows.

Figure 1: Calculation Java class

Figure 02: Java class with the main method

Calculation class has two abstract methods called sum and sub. The Test class extends the Calculation class. Therefore, this class provides implementations for both sum and sub-methods. In the main program, there is an object of type Test, and the sum and sub-methods are called. Finally, the summation and subtracted values are displayed on the console. Even though the abstract class contains only abstract methods in this example, it is also possible for that class to have non-abstract methods.

What is final Class in Java 

A class declared with the “final” keyword is a final class. It is a way of restricting the user from accessing the class. In other words, it is not possible to extend a final class. Therefore, other classes cannot access the properties and methods of the final class or create objects using a final class.

Figure 3: Vehicle class

Figure 4: Car class

Vehicle is a final class. It has the method run. Car class extends Vehicle class but cause errors as Vehicle class is final. In the main program, c is an object of Car, and that object calls the run method. As Vehicle is a final method, it is not possible to access that method. Therefore, we cannot execute the program.

Difference Between abstract Class and final Class in Java

Definition

An abstract class is a class declared with an abstract keyword, which is a collection of abstract and non-abstract methods. But, the final class is a class declared with the final keyword, which restricts other classes from accessing it. Thus, this is the main difference between abstract class and final class in Java

Keyword

Moreover, abstract class use the “abstract” keyword while final class use the “final” keyword.

Usage

An abstract class helps to achieve abstraction while the final class helps to restrict other classes from accessing its properties and methods. Thus, this is the functional difference between abstract class and final class in Java.

Conclusion

In brief, the abstract class and final class are two concepts in Java. The main difference between abstract class and final class in Java is that abstract class is a class with abstract and non-abstract methods, which allows accomplishing abstraction, while final class is a class that restricts the other classes from accessing its data and methods.

References:

1.“Abstract Class in Java – Javatpoint.” Www.javatpoint.com, Available here.
2.“Final Keyword in Java – Javatpoint.” Www.javatpoint.com, Available here.