Discuss scenarios where the final keyword significantly impacts the design of a Java program.

The final keyword is an important design tool in Java that helps create more secure, predictable, and maintainable applications. It can be applied to variables, methods, and classes to restrict modification, inheritance, or reassignment. Its proper use supports immutability, thread safety, and controlled object-oriented design.

Key Points: • final variables can be assigned only once, making them ideal for constants and immutable objects. • final methods prevent overriding, ensuring that critical business logic remains unchanged in subclasses. • final classes cannot be extended, which protects their behavior and helps maintain design integrity.

Example: The String class is declared as final in Java. This prevents inheritance and preserves its immutable nature, making it safe to use in collections, caching, and multi-threaded environments.

Code Example:

public final class Configuration {

    private final String appName;

    public Configuration(
            String appName) {

        this.appName = appName;
    }

    public final String getAppName() {

        return appName;
    }
}

In this example: • The class cannot be extended. • The field cannot be reassigned after initialization. • The method cannot be overridden.

Common Design Scenarios: • Creating immutable classes such as String-like objects. • Protecting security-sensitive classes from modification. • Defining application constants. • Preventing accidental method overriding. • Improving thread safety by using immutable state.

Interview Tip: A concise interview answer is: The final keyword significantly impacts design by enforcing immutability, preventing inheritance, and protecting critical methods from being overridden. It is commonly used for constants, immutable objects, thread-safe designs, and classes whose behavior must remain fixed throughout the application lifecycle.