// Queue using an integer array
public class Queue
{
  // Constant specifying the maximum queue size
  public static final int DEFAULT_SIZE = 1000;

  // Internal (hidden) representation is an array
  private int[] q;
  
  // Index of front of queue
  private int qFront;
  
  // Number of elements in this queue
  private int qSize;

  // Maximum size of this queue
  private int maxSize;

  // Construct a queue of default size
  public Queue() { this( DEFAULT_SIZE ); }

  // Construct a queue
  public Queue( int size ) {
    this.q = new int[size];
    this.qFront = this.qSize = 0;
    this.maxSize = size;
  }

  // Determine if this queue is empty
  public boolean isEmpty() {
    return ( this.qSize == 0 );
  }
  
  // Add an element to the end of this queue
  public void add( int x ) {
    if ( this.qSize < this.maxSize ) {
      int i = ( this.qFront + this.qSize ) % this.maxSize;
      this.q[i] = x;
      this.qSize++;
      System.out.println( "ADDED " + x );
    } else {
      // ERROR
      System.out.println( "FULL - CANNOT ADD " + x );
    }
  }
  
  // Remove an element from the head of this queue
  public int remove() {
    if ( this.qSize == 0 ) {
      // ERROR
      System.out.println( "EMPTY!" );
      return -1;
    } else {
      int x = this.q[this.qFront];
      this.q[this.qFront] = 0;
      this.qFront = ( this.qFront + 1 ) % this.maxSize;
      this.qSize--;
      System.out.println( "REMOVED " + x );
      return x;
    }
  }

  public static void main(String[] args) {
    System.out.println( "Default queue size is " + Queue.DEFAULT_SIZE );

    Queue q1 = new Queue(3);   // 7

    if ( q1.isEmpty() ) {
      q1.add( 12 );
      q1.add( 34 );
      int x = q1.remove();
      q1.add( 36 );
      q1.add( 17 );
      q1.add( 14 );
      x = q1.remove();
      x = q1.remove();
      x = q1.remove();
      x = q1.remove();
    }
  }

}