What is the purpose of the ‘final’ keyword in Java?

In Java, the keyword “final” can be used to modify classes, methods, and variables, serving the following purposes:

1. A class that is marked as final cannot be inherited by any other classes, therefore preventing any subclasses. This helps to safeguard the integrity and security of the class by disallowing any modifications from other classes.
2. Methods modified with ‘final’ cannot be overridden by subclasses, meaning that subclasses cannot modify the implementation of the method. This helps prevent other classes from altering the method and ensures that the method’s behavior remains unchanged.
3. Final variables: Variables that are marked as final are constants, meaning their values cannot be changed. Once they are assigned an initial value, they cannot be altered. Final variables are typically named with uppercase letters and are commonly used to define constants.

Using the final keyword can enhance program performance, as the compiler optimizes variables marked as final by replacing constants with their literal values directly, avoiding runtime calculations. In addition, variables marked as final provide stricter constraints, ensuring that their values won’t be accidentally modified, thus improving the robustness and maintainability of the program.