What are Final Class in Java with Examples

In the world of Java programming, the keyword "final" holds significant importance, especially when it comes to classes. Final classes in Java provide developers with a powerful tool for designing robust and secure software. In this comprehensive guide, we will delve into the intricacies of final classes, exploring their definition, creation, applications, advantages, drawbacks, and differences from final methods.

Introduction

Java, as an object-oriented programming language, allows developers to create classes that serve as blueprints for objects. These classes can be extended and modified to suit various requirements. However, there are scenarios where developers need to restrict the inheritance of a class or prevent it from being subclassed altogether. This is where final classes come into play.

What is the Final Class in Java?

A final class in Java cannot be subclassed. In other words, it is the endpoint of the inheritance hierarchy, and no other class can extend it. When a class is declared as final, it signifies that its implementation is complete and cannot be further modified by inheritance.

How to Create Final Classes in Java?

Creating a final class in Java is straightforward. Simply use the "final" keyword before the class declaration. For example:

java

final class FinalClass {
    // Class members and methods
}

By declaring the class as final, you explicitly prevent any other class from extending it.

Uses of Final Classes in Java with Examples

Final classes find numerous applications in Java development. They are commonly used in scenarios where:

1. Security is paramount: Final classes ensure that critical components of the system cannot be altered or compromised by subclasses.

1. Performance optimization: By sealing the implementation, final classes allow the compiler to perform optimizations, leading to better runtime performance.
   

2. API design: Final classes are often employed in API design to enforce contracts and prevent unintended subclassing, thereby promoting stability and consistency.

Let's illustrate these use cases with an example:

java

final class Configuration {
    private final String databaseUrl;

    public Configuration(String databaseUrl) {
        this.databaseUrl = databaseUrl;
    }

    // Methods for accessing and manipulating configuration settings
}

The Configuration class encapsulates sensitive information such as database URLs in this example. By making it final, we ensure its implementation cannot be tampered with, thus enhancing security.

Final Keyword in Java

Apart from final classes, the "final" keyword is also used to denote other entities in Java, such as variables and methods. When applied to variables, it indicates that the variable's value cannot be changed once assigned. Similarly, when applied to methods, it signifies that subclasses cannot override the method.

Advantages and Drawbacks of Final Classes

Final classes offer several advantages:

1. Security: Final classes provide a level of security by preventing unauthorized modifications to critical components.

1. Performance: They enable compiler optimizations, resulting in improved runtime performance.

1. API design: Final classes promote API stability and consistency by restricting subclassing.

However, final classes also have drawbacks:

1. Reduced flexibility: Once a class is declared final, its design becomes rigid, making it challenging to adapt to changing requirements.
   

2. Limited extensibility: Subclassing is entirely prohibited for final classes, limiting their potential for reuse and extension.

Difference between Final Class & Final Method

While both final classes and final methods serve to restrict modification, they operate at different levels of abstraction:

Final classes prevent inheritance altogether, sealing the implementation of the entire class.

Final methods, on the other hand, allow subclassing but restrict the overriding of specific methods within the class.

Conclusion

Final classes in Java play a crucial role in ensuring code security, performance optimization, and API stability. By understanding how to create and utilize final classes effectively, developers can design robust and maintainable software systems.

FAQs

What is the difference between a final method and a final class in Java?

A final method prevents overriding in subclasses, while a final class prevents subclassing altogether.

Can final classes have static methods in Java?

Yes, final classes can have static methods. The "final" keyword only restricts subclassing, not the inclusion of static methods.

Can the final be null in Java?

No, the "final" keyword in Java ensures that the value assigned to a final variable cannot be changed after initialization, including being set to null.

Why is the String class final in Java?

The String class is made final in Java to ensure its immutability, preventing subclasses from modifying their behavior and maintaining string integrity.

Which class cannot be a subclass in Java?

Any class declared as final cannot be subclassed in Java, thus serving as the endpoint of the inheritance hierarchy.