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

In Java 21, the LinkedHashSet class introduced the getFirst() method, allowing you to retrieve the first element of the collection. 

Table of Contents

1. Introduction
2. getFirst Method Syntax
3. Examples
   • Retrieving the First Element in LinkedHashSet
   • Handling an Empty LinkedHashSet
4. Real-World Use Case
   • Use Case: Task Management System
5. Conclusion

Introduction

The LinkedHashSet.getFirst() method is a new addition in Java 21 that allows you to retrieve the first element of the LinkedHashSet. This method is useful when you need to access the first element of the collection while maintaining the order of insertion.

getFirst() Method Syntax

The syntax for the getFirst method is as follows:

public E getFirst()

• The method does not take any parameters.
• The method returns the first element of the LinkedHashSet.

Examples

Retrieving the First Element in LinkedHashSet

The getFirst method can be used to retrieve the first element of a LinkedHashSet.

Example

import java.util.LinkedHashSet;

public class GetFirstExample {
    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");

        // Retrieving the first element
        String firstAnimal = animals.getFirst();

        // Printing the first element
        System.out.println("First animal: " + firstAnimal);
    }
}

Output:

First animal: Lion

Handling an Empty LinkedHashSet

When the LinkedHashSet is empty, calling getFirst will result in an exception. Therefore, it's important to check if the set is empty before calling this method.

Example

import java.util.LinkedHashSet;

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

        // Checking if the LinkedHashSet is empty before retrieving the first element
        if (!animals.isEmpty()) {
            String firstAnimal = animals.getFirst();
            System.out.println("First animal: " + firstAnimal);
        } else {
            System.out.println("The LinkedHashSet is empty.");
        }
    }
}

Output:

The LinkedHashSet is empty.

Real-World Use Case

Use Case: Task Management System

In a task management system, tasks are often managed in the order they are added. There are scenarios where the first task needs to be retrieved for processing. The getFirst 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");

        // Retrieving the first task
        if (!tasks.isEmpty()) {
            String firstTask = tasks.getFirst();
            System.out.println("First task to be done: " + firstTask);
        } else {
            System.out.println("No tasks available.");
        }
    }
}

Output:

First task to be done: Complete project report

Conclusion

The LinkedHashSet.getFirst() method introduced in Java 21 provides a way to retrieve the first element of a LinkedHashSet. By understanding how to use this method, you can efficiently access the first element while maintaining the order of elements in your collections. This method is useful for accessing the first inserted element in a predictable manner, 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 retrieving tasks for processing.