Q 31 - Final Keyword

[AmjustGettingStarted]

What is the final keyword in Java?

[HARSHITH-MV]

🔒 Purpose of final in Java

The final keyword prevents further modification. It’s Java’s way of saying “this must stay as it is.” Here's how it's used across different contexts:

1. Final Variables

• Once assigned, cannot be changed.
• Acts as a constant—typically used for fixed values (like PI or configuration values).

final int MAX_USERS = 100; // Can't be reassigned later

2. Final Methods

• A method declared final cannot be overridden by subclasses.
• Useful when you want to lock in behavior and prevent subclasses from altering it.

class Bank {
    final void calculateInterest() {
        // Fixed calculation logic
    }
}

3. Final Classes

• A class marked final cannot be subclassed.
• Prevents inheritance, often used for security or design reasons when modification would be risky.

final class Utility {
    // Static helper methods
}

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💡 Why Use final?

• Safety: Prevent unintended changes to critical logic or data.
• Design clarity: Indicates immutability or fixed behavior by intent.
• Performance: In some cases, allows compiler optimizations.

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