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.

Comments

Post a Comment

Popular posts from this blog

Java 8 DoubleFunction Example

In this blog post, I will be explaining how the Java 8 functional interface DoubleFunction works. To know more about functional interfaces, you can refer  this  blog post. Edit The   DoubleFunction interface provides a method called apply . It accepts a single parameter of double data type. It returns a result of any data type. So it basically applies the logic in the apply method to the input parameter and returns the result. The DoubleFunction interface is a specialization of the Function interface. While the Function interface accepts any data type, the DoubleFunction interface accepts a long value. To see an example of the Function interface, refer to  this  blog post. DoubleFunction Interface that returns an Integer Consider the following code snippet: DoubleFunction<Integer> integerRetriever = input -> new Double(input).intValue();Double input = 4.8;System.out.println("Integer Value "+integerRetriever.apply(input) );   Here, we have written a   Doubl...
Read more

How to convert a List to a Set

In this blog post ,I will be showing you how you can convert a List to a Set. Consider the following code snippet: public class ListToSetDemo {public static void main(String[] args) {List<Integer> list = Arrays.asList(5,3,11,15,9);//Method 1Set<Integer> set = new HashSet<Integer>(list);System.out.println("Set is "+set);//method 2Set<Integer> set2 = new HashSet<Integer>();set2.addAll(list);System.out.println("Set is "+set2);}} This code demonstrates two ways to convert a List to a Set. Method 1 Here, we are creating a new HashSet . We are invoking the constructor that accepts a Collection object. Here, we are passing in the input list to this constructor.   Method 2 Here again, we are creating a new HashSet . However, we are using the default constructor. We are then invoking the addAll method and passing in the input list.   When you run this code, it will print the following output: Set is [3, 5, 9, 11, 15]Set is [3, 5, 9, 1...
Read more

ArrayList Vs LinkedList

In this blog post, I will be comparing the ArrayList and LinkedList classes. I will be explaining how they are similar, how they are different and when you should use which.   Similarities: Both are Collections and implement the List interface Both are used to store a dynamic number of elements (Primitive or Object type) Differences ArrayList uses an array data structure internally to store the data. A LinkedList on the other hand, uses a doubly linked list internally as the data structure to store data. If you are not familiar with what a Linked List data structure is, you can refer this link . When you need to insert or delete data from the bottom of the List, an ArrayList is faster. If you need to insert or delete an element from the middle of the list,  a LinkedList is faster. An ArrayList  uses an array to store the data internally. So when you insert or delete an element from the bottom of the list, this does not affect the array. However if you insert or delete an element...
Read more