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package us.ihmc.simulationconstructionset.gui;

//import com.sun.java.swing.SwingUtilities;  //old package name
import javax.swing.SwingUtilities;

/**
 * An abstract class that you subclass to perform GUI-related work in a dedicated thread. For
 * instructions on using this class, see
 * http://java.sun.com/products/jfc/swingdoc-current/threads2.html
 */
public abstract class SwingWorker
{
   private Object value; // see getValue(), setValue()
   @SuppressWarnings("unused")
   private Thread thread;

   /**
    * Class to maintain reference to current worker thread under separate synchronization control.
    */
   private static class ThreadVar
   {
      private Thread thread;

      ThreadVar(Thread t)
      {
         thread = t;
      }

      synchronized Thread get()
      {
         return thread;
      }

      synchronized void clear()
      {
         thread = null;
      }
   }

   private ThreadVar threadVar;

   /**
    * Get the value produced by the worker thread, or null if it hasn't been constructed yet.
    */
   protected synchronized Object getValue()
   {
      return value;
   }

   /**
    * Set the value produced by worker thread
    */
   private synchronized void setValue(Object x)
   {
      value = x;
   }

   /**
    * Compute the value to be returned by the get method.
    */
   public abstract Object construct();

   /**
    * Called on the event dispatching thread (not on the worker thread) after the
    * construct method has returned.
    */
   public void finished()
   {
   }

   /**
    * A new method that interrupts the worker thread. Call this method to force the worker to abort
    * what it's doing.
    */
   public void interrupt()
   {
      Thread t = threadVar.get();
      if (t != null)
      {
         t.interrupt();
      }

      threadVar.clear();
   }

   /**
    * Return the value created by the construct method. Returns null if either the
    * constructing thread or the current thread was interrupted before a value was produced.
    *
    * @return the value created by the construct method
    */
   public Object get()
   {
      while (true)
      {
         Thread t = threadVar.get();
         if (t == null)
         {
            return getValue();
         }

         try
         {
            t.join();
         }
         catch (InterruptedException e)
         {
            Thread.currentThread().interrupt(); // propagate

            return null;
         }
      }
   }

   /**
    * Start a thread that will call the construct method and then exit.
    */
   public SwingWorker()
   {
      final Runnable doFinished = new Runnable()
      {
         @Override
         public void run()
         {
            finished();
         }
      };

      Runnable doConstruct = new Runnable()
      {
         @Override
         public void run()
         {
            try
            {
               setValue(construct());
            }
            finally
            {
               threadVar.clear();
            }

            SwingUtilities.invokeLater(doFinished);
         }
      };

      Thread t = new Thread(doConstruct, "SCSSwingWorkerConstruct");
      threadVar = new ThreadVar(t);
      t.start();
   }
}