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Final Variable in Java

Updated: Dec 16, 2023

Final Variable in Java

In Java, the final keyword is a powerful tool that provides immutability and constant values to your code. Final variables can be applied to fields, methods, and classes, and they play a crucial role in maintaining code integrity and security. In this comprehensive blog post, we'll dive deep into the concept of final variable in Java, their various use cases, and provide real-world examples to illustrate their significance.

What Are Final Variables?

In Java, a final variable is a variable that cannot be reassigned once it has been assigned a value. This makes it a constant or immutable variable. Once a final variable is assigned a value, it cannot be modified, providing predictability and preventing unintended changes to critical data.

Final Fields

Real-World Example: Mathematical Constants public class MathConstants {

public static final double PI = 3.14159265359;

public static final double E = 2.71828182846;


In this example, we've defined two final fields PI and E, which represent the mathematical constants π (pi) and e (Euler's number). These constants should never change during program execution, making them ideal candidates for final fields.

Core Java Programming

Java Back-End Development

Final Methods

In addition to final fields, the final keyword can also be applied to methods. A final method cannot be overridden by any subclass, ensuring that the behavior of a method remains consistent across the entire inheritance hierarchy.

Real-World Example: Security public class AuthenticationManager {

public final boolean authenticate(String username, String password) {

// Code for authentication

// ...



class SecureAuthenticationManager extends AuthenticationManager {


public boolean authenticate(String username, String password) {

// Override not allowed

// ...



In this example, the authenticate method in the AuthenticationManager class is declared as final to prevent subclasses from changing its behavior. This is crucial for maintaining security standards in authentication systems.

Final Classes

A final class is a class that cannot be extended or subclassed. Marking a class as final ensures that it cannot be modified or extended by other classes, preserving its intended functionality.

Real-World Example: String Class

The java.lang.String class in Java is a final class. You cannot create a subclass of String. This is because the String class is designed to be immutable, and allowing subclasses could compromise this immutability.

Benefits of Using Final Variables

Using final variables in your code offers several benefits:

Predictability: Final variables ensure that the assigned value remains constant throughout the program's execution, reducing the risk of unexpected changes.

Security: Final methods and classes can prevent unauthorized or unintended modifications, enhancing the security of your code.

Performance: Final fields can be optimized by the compiler, potentially resulting in faster code execution.

Thread Safety: Final variables can contribute to thread safety when used correctly, as they prevent concurrent modifications.


Final variables in Java are a valuable tool for ensuring immutability, predictability, and code integrity. By marking fields, methods, or classes as final, you can make your code more robust and secure. Real-world examples, such as mathematical constants, authentication methods, and built-in Java classes like String, demonstrate the practical applications of final variables in various contexts.

Understanding when and how to use final variables is essential for writing clean, reliable, and maintainable Java code. Incorporating them into your code base can lead to more robust and secure Java applications.

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