Notes

final keyword is used to provide restriction to classes, methods or variables, ensuring immutability.

uses

• variables - make then constant
• -methods - cannot be overridden
• classes - cannot be inherited.

class Example {
    final int MAX_VALUE = 100; // Final instance variable, initialized at declaration
    final double PI; // Blank final variable

    Example() {
        PI = 3.14159; // Initialized in constructor
    }

    void modify() {
        // MAX_VALUE = 200; // Compilation error: Cannot assign a value to final variable
        // PI = 3.14; // Compilation error
    }
}

class Main {
    public static void main(String[] args) {
        final int localVar = 10; // Final local variable
        // localVar = 20; // Compilation error
        System.out.println(localVar); // Output: 10

        Example ex = new Example();
        System.out.println(ex.MAX_VALUE); // Output: 100
        System.out.println(ex.PI); // Output: 3.14159
    }
}

• final prevents reassigning the reference but the objects internal state can still be modified.