shaggy/Queue.java

   1 public class Queue {
   2         QElement        head, tail;
   3
   4         Queue() {
   5                 head = tail = null;
   6                 }
   7
   8         public synchronized void append( Object o ) {
   9                 if( tail == null )
  10                         head = tail = new QElement( o );
  11                 else {
  12                         tail.next = new QElement( o );
  13                         tail = tail.next;
  14                         }
  15                 notifyAll();
  16                 }
  17
  18         public synchronized Object get() {
  19                 try {
  20                         while( head == null )
  21                                 wait();
  22                         } catch( InterruptedException ie ) {
  23                                 return null;
  24                         }
  25
  26                 Object          o = head.theData;
  27                 head = head.next;
  28
  29                 if( head == null )
  30                         tail = null;
  31                 return o;
  32                 }
  33
  34   public boolean empty() {
  35     return( head == null );
  36   }
  37         }
  38
  39 class QElement {
  40         QElement        next;
  41         Object          theData;
  42
  43         QElement( Object o ) {
  44                 next = null;
  45                 theData = o;
  46                 }
  47         }
  48