When Should You Use a `final class` in Java?

Using "final class" in Java

Declaring a class as "final" in Java has a specific purpose: it restricts the ability to extend or inherit from that class. This notion might seem counterintuitive in object-oriented programming, where inheritance is a fundamental concept. However, there are scenarios where it can be beneficial.

When to Utilize "final class"?

Programmers utilize "final class" when they wish to prevent subclassing for specific classes. For instance, a class representing an abstract entity or a core library class should not be extensible. Declaring such classes as final ensures that their behavior won't be modified through inheritance. Additionally, "final class" can improve performance, as the JVM can optimize code paths that are known not to change due to subclassing.

Does "final class" Conflict with OOP Principles?

While declaring a class as "final" limits its extensibility, it does not eliminate its object-oriented characteristics. Objects of final classes can still be created, manipulated, and interact with other objects within the program. However, they cannot be extended to create specialized subclasses. This restriction serves to enforce the clarity and stability of the class's design.

Examples

• The Java String class is declared final, preventing any subclasses from modifying its immutable behavior.
• The Math class is also final, ensuring that its mathematical functions cannot be overridden.
• System classes such as Thread and Object are final to provide a stable foundation for the Java runtime.

Conclusion

Declaring a class as final is not commonly employed in every program, but it is a valuable tool for certain situations. By understanding its purpose and benefits, programmers can effectively utilize "final class" to maintain code consistency, performance, and security in their Java applications.

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