Unlocking the Power of Java: Understanding the Final Keyword

The Unchangeable Truth

In Java, the final keyword is more than just a declaration – it’s a promise of immutability. When used with variables, methods, and classes, final ensures that once a value is assigned, it cannot be changed. This fundamental concept is crucial to understanding Java’s architecture.

Variables Set in Stone

Imagine trying to alter a constant – it’s a futile effort. In Java, declaring a variable as final means its value is locked in place. Attempting to reassign a new value will result in a compilation error.

public class Demo {
    public static final int AGE = 25;
    
    public static void main(String[] args) {
        AGE = 30; // Compilation error: cannot assign a value to final variable AGE
    }
}

Methods Carved in Granite

Before diving into final methods and classes, it’s essential to grasp Java Inheritance. A final method is one that cannot be overridden by a child class. This means that once a method is declared final, its implementation is set in stone.

public class FinalDemo {
    public final void display() {
        System.out.println("This is the final method");
    }
}

public class Main extends FinalDemo {
    public void display() { // Compilation error: cannot override final method from FinalDemo
        System.out.println("Trying to override the final method");
    }
    
    public static void main(String[] args) {
        Main main = new Main();
        main.display();
    }
}

Classes That Stand Alone

In Java, a final class is one that cannot be inherited by another class. This means that a final class is a self-contained unit that cannot be extended or modified.

public final class FinalClass {
    public void doSomething() {
        System.out.println("This is a final class");
    }
}

public class Main extends FinalClass { // Compilation error: cannot inherit from final FinalClass
    public static void main(String[] args) {
        Main main = new Main();
        main.doSomething();
    }
}

The Final Verdict

In summary, the final keyword is a powerful tool in Java that ensures immutability and prevents unwanted changes. By understanding how final variables, methods, and classes work, you’ll be better equipped to write robust and efficient code.