Queue: The first item inserted is the first to be removed (FIFO) : Your Queue « Collections « Java Tutorial

1. Java Tutorial
2. Collections
3. Your Queue

class Queue {
  private int maxSize;

  private int[] queArray;

  private int front;

  private int rear;

  private int nItems;

  public Queue(int s) {
    maxSize = s;
    queArray = new int[maxSize];
    front = 0;
    rear = -1;
    nItems = 0;
  }

  public void insert(int j) {
    if (rear == maxSize - 1)
      rear = -1;
    queArray[++rear] = j;
    nItems++;
  }


  public int remove() {
    int temp = queArray[front++];
    if (front == maxSize)
      front = 0;
    nItems--;
    return temp;
  }

  public int peekFront() {
    return queArray[front];
  }

  public boolean isEmpty() {
    return (nItems == 0);
  }

  public boolean isFull() {
    return (nItems == maxSize);
  }

  public int size() {
    return nItems;
  }
}

public class MainClass {
  public static void main(String[] args) {
    Queue theQueue = new Queue(5); // queue holds 5 items

    theQueue.insert(10); // insert 4 items
    theQueue.insert(20);
    theQueue.insert(30);
    theQueue.insert(40);

    theQueue.remove(); // remove 3 items
    theQueue.remove(); // (10, 20, 30)
    theQueue.remove();

    theQueue.insert(50); // insert 4 more items
    theQueue.insert(60); // (wraps around)
    theQueue.insert(70);
    theQueue.insert(80);

    while (!theQueue.isEmpty()) { // all items
      int n = theQueue.remove(); // (40, 50, 60, 70, 80)
      System.out.print(n);
      System.out.print(" ");
    }
    System.out.println("");
  }
}

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