final Keyword

Employee ID. Once assigned, the ID should never change.

Real-World Problem

Imagine an Employee Management System where every employee has a unique Employee ID. Once assigned, the ID should never change. Why Do We Need final? The final keyword prevents modification, inheritance, or method overriding, helping create secure and immutable code. What is final?

The final keyword is used to restrict changes to variables, methods, and classes.

Uses of final

Final Variable Its value can be assigned only once.

Final Method Cannot be overridden by child classes.

Final Class Cannot be inherited by another class.

final freezes things: constants, un-reassignable references, and un-extendable classes/methods.

final class MathUtil {           // cannot be subclassed
    static final double PI = 3.14159; // compile-time constant

    final int factor;            // must be set once, then fixed
    MathUtil(int factor) { this.factor = factor; }

    final int scale(int n) {     // cannot be overridden
        return n * factor;
    }
}