In the previous screen, we saw how to implement a queue using the LinkedList class in Java. Another common way to implement a queue is using arrays.

Array Implementation of Queues

The array implementation of queues involves using an array to store the items in the queue. Two pointers, front and rear, are used to keep track of the first and last elements of the queue, respectively.

Here's an example of how to implement a queue using an array in Java:

1import java.util.Arrays;
2
3public class ArrayQueue {
4  private static final int DEFAULT_CAPACITY = 10;
5  private int[] queue;
6  private int front;
7  private int rear;
8
9  public ArrayQueue() {
10    queue = new int[DEFAULT_CAPACITY];
11    front = -1;
12    rear = -1;
13  }
14
15  // Other methods
16}

In this implementation, we have an array queue to store the elements, and front and rear pointers to keep track of the first and last elements, respectively. The DEFAULT_CAPACITY is used to specify the initial capacity of the array, and it can be adjusted as needed.

To enqueue an element, we increment the rear pointer and add the element to the queue. If the rear pointer exceeds the array size, we resize the array to accommodate more elements.

To dequeue an element, we increment the front pointer and return the element at the front position. If the front pointer exceeds the rear, it means the queue is empty.

The advantage of the array implementation is that it provides constant-time access to the front and rear elements. However, it has a fixed size and can run out of space if more elements are added than the initial capacity.

Now that we have seen the array implementation of queues, let's move on to the next topic: linked list implementation of queues.

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}

import java.util.Arrays;

​

public class ArrayQueue {

  private static final int DEFAULT_CAPACITY = 10;

  private int[] queue;

  private int front;

  private int rear;

​

  public ArrayQueue() {

    queue = new int[DEFAULT_CAPACITY];

    front = -1;

    rear = -1;

  }

​

  public void enqueue(int item) {

    if (rear == queue.length - 1) {

      // Queue is full, resize the array

      queue = Arrays.copyOf(queue, queue.length * 2);

    }

    queue[++rear] = item;

    if (front == -1) {

      front = 0;

    }

  }

​

  public int dequeue() {

    if (front == -1 || front > rear) {

      // Queue is empty

      throw new NoSuchElementException();