import java.util.*;

/**
 * <p><code>class Queue</code> is a simple implementation of a queue
 * data structure. </p>
 *
 * @author G.D.Thurman
 * @version 99.09.26
 */

public class Queue implements Csxxx_Containers {
   private Vector elems;

   public Queue() { this(DFLT_NELEMENTS); }
   public Queue(int len) { elems = new Vector(len); }

   public void enqueue(Object elem)  { elems.addElement(elem); }
   public Object dequeue() {  
      Object obj = front(); 
      if (obj != null) elems.removeElementAt(0);
      return obj;
   }
   public Object front() { 
      return elems.size() == 0 ? null : elems.elementAt(0); 
   }
   /* interfaces */
   public int capacity() { return elems.capacity(); }
   public int size() { return elems.size(); }
   public boolean isEmpty() { return elems.size() == 0; }
   public boolean isFull() { return elems.size() == elems.capacity(); }
   public void clear()  { elems.removeAllElements(); }
   public String toString() {
      int size = elems.size();
      String s = new String("queue contents:" + "\n" +
                            "===============\n");
      for (int i = 0; i < size; i++)
         s += "\t" + elems.elementAt(i) + "\n"; 
      s += "size: " + elems.size() + "; capacity: " + elems.capacity();
      return s;
   }

   public static void main(String[] argv) {
      Queue q = new Queue();
      for (int i = 0; i < argv.length; i++) q.enqueue(argv[i]);
      System.out.println(q);
      if (!q.isEmpty()) {
         System.out.println("\ndequeue: " + q.dequeue());
         System.out.println("front: " + q.front());
         System.out.println("size: " + q.size());
         System.out.println("capacity: " + q.capacity());
      }
      q.clear();
      System.out.println("\n*** queue cleared\n\n" + q);
   }
}