Java ArrayDeque addAll() Method

The ArrayDeque class in Java provides the addAll(Collection<? extends E> c) method to insert all elements from a specified collection into the deque. This guide will cover the method's usage, explain how it works, and provide examples to demonstrate its functionality using tasks in a task management system.

Table of Contents

1. Introduction
2. addAll Method Syntax
3. Examples
   • Adding All Elements from a Collection to an ArrayDeque
   • Handling an Empty Collection
4. Real-World Use Case
   • Use Case: Task Management System
5. Conclusion

Introduction

The ArrayDeque.addAll(Collection<? extends E> c) method is used to add all elements from a specified collection to the deque. This method is useful when you need to bulk add multiple elements to the deque.

addAll Method Syntax

The syntax for the addAll method is as follows:

public boolean addAll(Collection<? extends E> c)

• The method takes a single parameter c of type Collection<? extends E>, which is the collection containing elements to be added to the deque.
• The method returns a boolean value: true if the deque was modified as a result of the call, false otherwise.

Examples

Adding All Elements from a Collection to an ArrayDeque

The addAll method can be used to insert all elements from a specified collection into an ArrayDeque.

Example

import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Collection;

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

        // Adding initial elements to the ArrayDeque
        tasks.add("Complete project report");

        // Creating a collection of tasks to add
        Collection<String> newTasks = new ArrayList<>();
        newTasks.add("Email client updates");
        newTasks.add("Prepare presentation");

        // Adding all elements from the collection to the ArrayDeque
        boolean isAdded = tasks.addAll(newTasks);

        // Printing the result of the addAll operation
        System.out.println("Were tasks added? " + isAdded);

        // Printing the ArrayDeque after addAll
        System.out.println("ArrayDeque after addAll: " + tasks);
    }
}

Output:

Were tasks added? true
ArrayDeque after addAll: [Complete project report, Email client updates, Prepare presentation]

Handling an Empty Collection

When the specified collection is empty, the addAll method returns false and the deque remains unchanged.

Example

import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Collection;

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

        // Adding initial elements to the ArrayDeque
        tasks.add("Complete project report");

        // Creating an empty collection of tasks to add
        Collection<String> emptyTasks = new ArrayList<>();

        // Attempting to add all elements from the empty collection to the ArrayDeque
        boolean isAdded = tasks.addAll(emptyTasks);

        // Printing the result of the addAll operation
        System.out.println("Were tasks added? " + isAdded);

        // Printing the ArrayDeque after attempting to addAll
        System.out.println("ArrayDeque after addAll: " + tasks);
    }
}

Output:

Were tasks added? false
ArrayDeque after addAll: [Complete project report]

Real-World Use Case

Use Case: Task Management System

In a task management system, you may need to add a group of tasks from another collection to the main task deque. The addAll method can help achieve this functionality efficiently.

Example

import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Collection;

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));

        // Creating a collection of new tasks to add
        Collection<Task> newTasks = new ArrayList<>();
        newTasks.add(new Task("Email client updates", 1));
        newTasks.add(new Task("Prepare presentation", 3));

        // Adding all tasks from the collection to the ArrayDeque
        boolean isAdded = tasks.addAll(newTasks);

        // Printing the result of the addAll operation
        System.out.println("Were tasks added? " + isAdded);

        // Printing the tasks in the ArrayDeque after addAll
        System.out.println("Tasks in ArrayDeque: " + tasks);
    }
}

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:

Were tasks added? true
Tasks in ArrayDeque: [Complete project report (Priority: 2), Email client updates (Priority: 1), Prepare presentation (Priority: 3)]

Conclusion

The ArrayDeque.addAll(Collection<? extends E> c) method in Java is used for adding multiple elements from a collection to an ArrayDeque. Understanding how to use this method allows you to efficiently manage collections and bulk insert elements into the deque, making it particularly useful in applications like task management systems where multiple tasks need to be added at once.