/************ 
  a linked queue that implements Iterable and extends LinkedQueue
  compile this in the same directory as Queue.java

  the demo program includes instructions I and F that use an
  iterator to print all queue entries: I with a while loop
  and F with a for-each loop  *************************************/

import java.util.*;

class QueueIterator implements Iterator {

  private Node current;
  public QueueIterator(Node c) {current = c;}

  public Object next() { 
     Object answer = current.getData(); 
     current = current.getNext();
     return answer;
  }
  public boolean hasNext() {return current != null;}
  public void remove() {;}

}

class ItQueue extends LinkedQueue implements Iterable {

   public Iterator iterator() { return new QueueIterator(front); }


   public static void main(String args[]) {
      Queue q = new ItQueue();
      testQueue((ItQueue) q);
   }

   public static void testQueue(ItQueue q) {
      boolean done = false;
      while (!done) {
         try {
           Scanner sc = new Scanner(System.in);
           System.out.print( q + "  ");
           System.out.println("\ncmds are F I + - Q: >>");
           String cmd = sc.next();
           String entry = null;
           char command = cmd.charAt(0);
           if (command == '+') entry = sc.next();
           switch (cmd.charAt(0)) {
              case 'Q': done = true; break; 
              case '+': q.enqueue(entry); break;
              case '-': q.dequeue(); break;
              case 'I': Iterator x = q.iterator();
                        while (x.hasNext())
                          System.out.print(x.next());
                        System.out.println();
                        break;
              case 'F': for (Object y: q) System.out.print(y);
                        System.out.println();
                        break;
           }
        } catch (Exception e) {
           System.out.println("Error " + e.toString());
        }
      }   
   }
}