ArrayQueue.java

import java.util.*;

class ArrayQueue {
  private String[] q;
  private int front;
  private int rear;
  private int size;
  
  ArrayQueue(int capacity) {
    front = 0;
    rear = 0;
    size = 0;
  }
  
  public int capacity() {
    return q.length;
  }
  
  public void enqueue(String s) {
    if (size == q.length)
      throw new QueueOverflowException();
    else {
      size++;
      q[rear] = s;
      rear++;
      if (rear == q.length) rear = 0;
    }
  }
  
  public String peek() {
    if(empty())
      throw new EmptyQueueException();
    else
      return q[front];
  }
  
  public String dequeue() {
    if(empty())
      throw new EmptyQueueException();
    else {
      size--;
      String value = q[front];
      q[front] = null;
      front++;
      if (front == q.length)
        front = 0;
      return value;
    }
  }
  
  public boolean empty() {
    return size == 0;
  }
}