Understanding Final Methods in Java: Definition and Usage

What is the final method in Java?

In Java, the final keyword can be applied to classes, methods, and variables, and it serves different purposes in each context. When it comes to methods, declaring a method as final means that the method cannot be overridden by subclasses. This is useful when you want to ensure that the specific implementation of a method remains unchanged in any derived class.

Example of a Final Method

Here’s a simple example to illustrate the use of a final method:

class Parent {
    // This method cannot be overridden in any subclass
    public final void display() {
        System.out.println("This is a final method.");
    }
}

class Child extends Parent {
    // This will cause a compile-time error
    // public void display() {
    //     System.out.println("Trying to override a final method.");
    // }
}

public class Main {
    public static void main(String[] args) {
        Child child = new Child();
        child.display(); // This will call the final method from Parent
    }
}

Key Points about Final Methods:

1. Cannot be Overridden: A final method cannot be overridden in any subclass, which helps in maintaining the behavior of the method.
2. Inheritance: You can still inherit a final method; it just cannot be changed.
3. Performance: In some cases, the use of final methods can lead to performance optimizations by the Java compiler, as it can make certain assumptions about the method's behavior.

Using final methods is a design choice that can help enforce certain behaviors in your class hierarchy.