Java ArrayDeque getFirst() Method

The ArrayDeque class in Java provides the getFirst() method to retrieve, but not remove, the first element of the deque.

Table of Contents

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

Introduction

The ArrayDeque.getFirst() method is used to retrieve, but not remove, the first element of the ArrayDeque. If the deque is empty, the method throws a NoSuchElementException.

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 deque.

Examples

Retrieving the First Element of the ArrayDeque

The getFirst method can be used to view the first element of an ArrayDeque.

Example

import java.util.ArrayDeque;

public class ArrayDequeGetFirstExample {
    public static void main(String[] args) {
        // Creating an ArrayDeque of Strings
        ArrayDeque<String> tasks = new ArrayDeque<>();

        // Adding elements to the ArrayDeque
        tasks.add("Complete project report");
        tasks.add("Email client updates");
        tasks.add("Prepare presentation");

        // Retrieving the first element of the ArrayDeque using getFirst
        String firstTask = tasks.getFirst();

        // Printing the first element of the ArrayDeque
        System.out.println("First task: " + firstTask);
    }
}

Output:

First task: Complete project report

Handling an Empty ArrayDeque

When the ArrayDeque is empty, the getFirst method throws a NoSuchElementException.

Example

import java.util.ArrayDeque;
import java.util.NoSuchElementException;

public class EmptyArrayDequeGetFirstExample {
    public static void main(String[] args) {
        // Creating an empty ArrayDeque of Strings
        ArrayDeque<String> tasks = new ArrayDeque<>();

        try {
            // Attempting to retrieve the first element of the empty ArrayDeque using getFirst
            String firstTask = tasks.getFirst();
            System.out.println("First task: " + firstTask);
        } catch (NoSuchElementException e) {
            System.out.println("ArrayDeque is empty: " + e.getMessage());
        }
    }
}

Output:

ArrayDeque is empty: null

Real-World Use Case

Use Case: Task Management System

In a task management system, you might need to check the highest-priority task without removing it from the deque. The getFirst method can be used to view the next task to be processed.

Example

import java.util.ArrayDeque;

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

        // Adding initial tasks to the ArrayDeque
        tasks.add(new Task("Complete project report", 2));
        tasks.add(new Task("Email client updates", 1));
        tasks.add(new Task("Prepare presentation", 3));

        // Retrieving the first task using getFirst
        Task nextTask = tasks.getFirst();

        // Printing the next task to be processed
        System.out.println("Next task to be processed: " + nextTask);
    }
}

class Task {
    private String description;
    private int priority;

    public Task(String description, int priority) {
        this.description = description;
        this.priority = priority;
    }

    @Override
    public String toString() {
        return description + " (Priority: " + priority + ")";
    }
}

Output:

Next task to be processed: Complete project report (Priority: 2)

Conclusion

The ArrayDeque.getFirst() method in Java is used for accessing the first element of a deque without removing it. Understanding how to use this method allows you to effectively manage and view the highest-priority elements in the deque, making it particularly useful in applications like task management systems where you need to check the next task to be processed without altering the deque.