Final Keyword in java

In Java, the final keyword is used to restrict changes. Once something is marked as final, it cannot be modified further. It can be applied in three main places: variables, methods, and classes.

1. Final Variable

A final variable acts like a constant — its value cannot be changed once assigned.

public class GRT{
    final int price = 15000;

    public void display(){
        GRT grt = new GRT();
        grt.price = 200;

        System.out.println(grt.price);
    }
}

Key point:

• You must assign value once
• After that, no reassignment allowed

2. Final Method
A final method cannot be overridden by subclasses.

class Parent {
    final void show() {
        System.out.println("This is final method");
    }
}

class Child extends Parent {
    // void show() { } ❌ Error: cannot override final method
}

Key point:

• Used when you want to prevent method overriding

3. Final Class
A final class cannot be extended (inherited).

final class A {
    void display() {
        System.out.println("Final class");
    }
}

// class B extends A { } ❌ Error: cannot inherit final class

Key point:

• Used when you want to stop inheritance