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 errorpublic 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.

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