Java Final Keyword Explained with Code Samples

In this article, I will be covering Java’s final keyword. I will be demonstrating the final keyword in Java with an example.

Introduction

You can use the final keyword with a method or instance field. When you use it with a method, it prevents the method from being overridden. When you use it with a field, it prevents the field from being modified.

Final Method

public class Base {




public final void show() {

System.out.println("In show”);

}




}

public class Sub extends Base {







// This method causes a compilation error

public void show() {

}

}

}

• Class Base has a method show which is marked as final
• Sub is a sub-class, it overrides show
• There is a compilation error in Sub as the final method cannot be overridden

Final Field

Declaring a variable as final prevents its contents from being modified. This means that you must initialize a final variable when it is declared.

The following code demonstrates a final field:

public void aMethod() {

final int d = 10;

d = 3; // compilation error

}

• The method aMethod has a field called d which is marked as final
• The method tries to set d to 3
• There is a compilation error since the final variable cannot be modified

Conclusion

So, in this article, we saw why final keyword is used in Java.