---

Final Keyword in Java

The final keyword in Java is used to restrict modification.
It can be applied to:

• Variables (values cannot be changed)
• Methods (cannot be overridden)
• Classes (cannot be inherited)

Final Variables

A variable declared final becomes constant — you must assign a value, and it cannot change after assignment.

Example:

    
    final int x = 10;
    // x = 20;  // ❌ Error: cannot assign a value to final variable
    
    

Final Reference Variable

If the variable is a reference type, the object it points to can still be modified, but the reference itself cannot change.

    
    final int[] arr = {1, 2, 3};
    arr[0] = 10;      // ✅ Allowed
    // arr = new int[5];  // ❌ Not allowed
    
    

Final Methods

A method marked final cannot be overridden by subclasses.

Example:

    
    class Animal {
        final void sound() {
            System.out.println("Animal sound");
        }
    }

    class Dog extends Animal {
        // void sound() {}  // ❌ Error: Cannot override final method
    }
    
    

Final Classes

A class declared as final cannot be extended.

Example:

    
    final class Vehicle {
        void run() {
            System.out.println("Vehicle is running");
        }
    }

    // class Car extends Vehicle {}  // ❌ Error: Cannot subclass final class
    
    

Summary Table

final Applied To	Meaning
Variable	Constant value (cannot be reassigned)
Method	Cannot be overridden
Class	Cannot be extended (no subclasses)

When to Use final

Use Case	Why
Constants	Ensure values like PI, MAX_LIMIT, etc. don’t change
Prevent Inheritance	Improve security and avoid misuse
Immutable Classes	Build classes like String, which can't be modified

---