lab9/act2/Troll.java

   1 /*
   2  * Troll.java
   3  *
   4  * $Id: Troll.java,v 1.1 2008/05/08 18:33:30 slf4878 Exp slf4878 $
   5  *
   6  * Revisions:
   7  *    $Log: Troll.java,v $
   8  *    Revision 1.1  2008/05/08 18:33:30  slf4878
   9  *    Now controls order of Woolies.
  10  *
  11  *    Revision 2.3  2006/10/17 18:48:23  vcss232
  12  *    test
  13  *
  14  *    Revision 2.2  2005/01/26 03:19:36  vcss232
  15  *    removed tabs (jeh)
  16  *
  17  *    Revision 2.1  2004/04/12 23:43:53  cs3
  18  *    moved the instance variables to the top of the class
  19  *    (bk)
  20  *
  21  *    Revision 2.0  2004/01/20 22:06:14  icss235
  22  *    *** empty log message ***
  23  *
  24  */
  25
  26
  27
  28 /**
  29  * A troll to guard a bridge. The troll simply passes requests from
  30  * woolies to his bridge. It is a placeholder for a later exercise.
  31  * <p>
  32  * Note
  33  * <ul>
  34  * <li>The troll gets entry permission; the woolie itself tells
  35  *     the bridge it is off.</li>
  36  * <li>The troll runs an independent thread to pull things off
  37  *     its queue. This thread runs forever, so the Troll objects
  38  *     must be a daemon thread.</li>
  39  * <ul>
  40  *
  41  * @author Unknown
  42  * @author Sarah Frisco
  43  * @author Ryan Hope
  44  */
  45 public class Troll {
  46
  47         /**
  48          * The bridge that this troll guards. The Bridge object
  49          * creates the troll object.
  50          */
  51         private Bridge myBridge;
  52         //A queue to keep track of the woolies trying to get on the bridge]
  53         //May 8, 08 slf4878
  54         private WoolieQueue queue;
  55
  56         /**
  57          * Create a troll. (Called by its Bridge object.)
  58          *
  59          * @param b the Bridge object associated with this Troll object
  60          */
  61         public Troll( Bridge b ) {
  62                 myBridge = b;
  63                 //Creates its own woolie queue
  64                 queue = new WoolieQueue();
  65         }
  66
  67         /**
  68          * Request permission to go on the bridge. This method is
  69          * called by a Woolie object. It just calls Bridge.enter().
  70          *
  71          * Postcondition:<ul>
  72          * <li>The woolie got permission and has entered the bridge.
  73          * </ul>
  74          */
  75         public synchronized void enterBridgePlease(Woolie woolie) {
  76                 System.out.println(woolie.getName() + " is talking to the troll");
  77                 queue.insert(woolie);
  78
  79                 //If the bridge is not full, and the woolie trying to get in is the next
  80                 //woolie in line, it allows the first woolie in the queue
  81                 //to get on the bridge.  It also removes that woolie from
  82                 //the queue May 8,08 slf4878
  83
  84                 while (true) {
  85                         if (!myBridge.isFull() && (woolie == queue.peek())) {
  86                                 myBridge.addWoolie();
  87                                 queue.remove();
  88                                 break;
  89                         } else {
  90                                 try {
  91                                         wait();
  92                                 } catch (InterruptedException e) {};
  93                         }
  94                 }
  95
  96         }
  97
  98         /**
  99          * Inform the troll that the caller (the woolie) is getting
 100          * off the bridge.
 101          */
 102         synchronized public void leave() {
 103                 myBridge.removeWoolie();
 104                 notifyAll();
 105         }
 106 }