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  | 16 |  |  package org.kuali.student.common.ui.client.mvc; | 
  | 17 |  |   | 
  | 18 |  |   | 
  | 19 |  |   | 
  | 20 |  |   | 
  | 21 |  |  import java.util.LinkedList; | 
  | 22 |  |   | 
  | 23 | 0 |  public class WorkQueue { | 
  | 24 | 0 |      public static abstract class WorkItem { | 
  | 25 | 0 |          private boolean canceled = false; | 
  | 26 |  |   | 
  | 27 |  |          public abstract void exec(final Callback<Boolean> onCompleteCallback); | 
  | 28 |  |   | 
  | 29 |  |          public boolean isCanceled() { | 
  | 30 | 0 |              return this.canceled; | 
  | 31 |  |          } | 
  | 32 |  |   | 
  | 33 |  |          protected void setCanceled(final boolean canceled) { | 
  | 34 | 0 |              this.canceled = canceled; | 
  | 35 | 0 |          } | 
  | 36 |  |      } | 
  | 37 |  |   | 
  | 38 | 0 |      private boolean running = false; | 
  | 39 | 0 |      private final LinkedList<WorkItem> queue = new LinkedList<WorkItem>(); | 
  | 40 |  |   | 
  | 41 | 0 |      private final Callback<Boolean> onCompleteCallback = new Callback<Boolean>() { | 
  | 42 |  |          @Override | 
  | 43 |  |          public void exec(final Boolean value) { | 
  | 44 | 0 |              processNext(); | 
  | 45 | 0 |          } | 
  | 46 |  |      }; | 
  | 47 |  |   | 
  | 48 |  |      public void clear() { | 
  | 49 | 0 |          for (final WorkItem item : queue) { | 
  | 50 | 0 |              item.setCanceled(true); | 
  | 51 |  |          } | 
  | 52 | 0 |          queue.clear(); | 
  | 53 | 0 |      } | 
  | 54 |  |   | 
  | 55 |  |      public boolean isRunning() { | 
  | 56 | 0 |          return this.running; | 
  | 57 |  |      } | 
  | 58 |  |   | 
  | 59 |  |      private void processNext() { | 
  | 60 | 0 |          WorkItem item = null; | 
  | 61 | 0 |          while (!queue.isEmpty() && (item = queue.removeFirst()) != null) { | 
  | 62 | 0 |              if (item.isCanceled()) { | 
  | 63 | 0 |                  item = null; | 
  | 64 |  |              } else { | 
  | 65 |  |                  break; | 
  | 66 |  |              } | 
  | 67 |  |          } | 
  | 68 | 0 |          if (item == null) { | 
  | 69 | 0 |              running = false; | 
  | 70 |  |          } else { | 
  | 71 | 0 |              item.exec(onCompleteCallback); | 
  | 72 |  |          } | 
  | 73 | 0 |      } | 
  | 74 |  |   | 
  | 75 |  |      public void submit(final WorkItem item) { | 
  | 76 | 0 |          queue.add(item); | 
  | 77 | 0 |          if (!running) { | 
  | 78 | 0 |              running = true; | 
  | 79 | 0 |              processNext(); | 
  | 80 |  |          } | 
  | 81 | 0 |      } | 
  | 82 |  |  } |