Java LinkedHashSet reversed() Method (Introduced in Java 21)

In Java 21, the LinkedHashSet class introduced the reversed() method, allowing you to obtain a reversed view of the elements in the collection.

Table of Contents

1. Introduction
2. reversed Method Syntax
3. Examples
   • Reversing the Order of Elements in LinkedHashSet
   • Handling an Empty LinkedHashSet
4. Real-World Use Case
   • Use Case: Task Management System
5. Conclusion

Introduction

The LinkedHashSet.reversed() method is a new addition in Java 21 that allows you to get a view of the elements in the LinkedHashSet in reverse order. This method is useful when you need to iterate over the elements in the reverse order of their insertion.

reversed() Method Syntax

The syntax for the reversed method is as follows:

public LinkedHashSet<E> reversed()

• The method does not take any parameters.
• The method returns a new LinkedHashSet containing the elements in reverse order.

Examples

Reversing the Order of Elements in LinkedHashSet

The reversed method can be used to get a reversed view of the elements in a LinkedHashSet.

Example

import java.util.LinkedHashSet;

public class ReversedExample {
    public static void main(String[] args) {
        // Creating a LinkedHashSet of Strings
        LinkedHashSet<String> animals = new LinkedHashSet<>();

        // Adding elements to the LinkedHashSet
        animals.add("Lion");
        animals.add("Tiger");
        animals.add("Elephant");

        // Getting the reversed LinkedHashSet
        LinkedHashSet<String> reversedAnimals = animals.reversed();

        // Printing the reversed LinkedHashSet
        System.out.println("Reversed LinkedHashSet: " + reversedAnimals);
    }
}

Output:

Reversed LinkedHashSet: [Elephant, Tiger, Lion]

Handling an Empty LinkedHashSet

When the LinkedHashSet is empty, calling reversed will return an empty LinkedHashSet.

Example

import java.util.LinkedHashSet;

public class ReversedEmptyExample {
    public static void main(String[] args) {
        // Creating an empty LinkedHashSet of Strings
        LinkedHashSet<String> animals = new LinkedHashSet<>();

        // Getting the reversed LinkedHashSet
        LinkedHashSet<String> reversedAnimals = animals.reversed();

        // Printing the reversed LinkedHashSet
        System.out.println("Reversed LinkedHashSet: " + reversedAnimals);
    }
}

Output:

Reversed LinkedHashSet: []

Real-World Use Case

Use Case: Task Management System

In a task management system, tasks are often managed in the order they are added. However, there are scenarios where you might want to review or process tasks in the reverse order. The reversed method can be used to achieve this functionality.

Example

import java.util.LinkedHashSet;

public class TaskManagementSystem {
    public static void main(String[] args) {
        // Creating a LinkedHashSet to store tasks
        LinkedHashSet<String> tasks = new LinkedHashSet<>();

        // Adding initial tasks
        tasks.add("Complete project report");
        tasks.add("Email client updates");
        tasks.add("Prepare presentation");

        // Getting the reversed LinkedHashSet of tasks
        LinkedHashSet<String> reversedTasks = tasks.reversed();

        // Printing the tasks in reverse order
        System.out.println("Tasks in reverse order: " + reversedTasks);
    }
}

Output:

Tasks in reverse order: [Prepare presentation, Email client updates, Complete project report]

Conclusion

The LinkedHashSet.reversed() method introduced in Java 21 provides a way to obtain a reversed view of the elements in a LinkedHashSet. By understanding how to use this method, you can efficiently manage and iterate over collections in reverse order. This method is useful for accessing elements in the reverse order of their insertion, making it a valuable tool for collection management in your Java applications. The real-world use case of a task management system illustrates the practical application of this method in processing tasks in reverse order.