door.java

这是java的一本书上的源代码

// Door.java
// Sends DoorEvents to DoorListeners when opened or closed
package com.deitel.jhtp5.elevator.model;

// Java core packages
import java.util.*;

// Deitel packages
import com.deitel.jhtp5.elevator.event.*;

public class Door  {

   // represent whether Door is open or closed
   private boolean open = false;

   // time before Door closes automatically
   public static final int AUTOMATIC_CLOSE_DELAY = 3000;

   // Set of DoorListeners
   private Set doorListeners;

   // location where Door opened or closed
   private Location doorLocation;

   // Door constructor instantiates Set for DoorListeners
   public Door()
   {
      doorListeners = new HashSet( 1 );
   }

   // add Door listener
   public void addDoorListener( DoorListener listener )
   {
      // prevent other objects from modifying doorListeners
      synchronized( doorListeners )
      {
         doorListeners.add( listener );
      }
   }

   // remove Door listener
   public void removeDoorListener( DoorListener listener )
   {
      // prevent other objects from modifying doorListeners
      synchronized( doorListeners )
      {
         doorListeners.remove( listener );
      }
   }

   // open Door and send all listeners DoorEvent objects
   public synchronized void openDoor( Location location )
   {
      if ( !open ) {

         open = true;

         // obtain iterator from Set
         Iterator iterator;
         synchronized( doorListeners )
         {
            iterator = new HashSet( doorListeners ).iterator();
         }

         // get next DoorListener
         while ( iterator.hasNext() ) {
            DoorListener doorListener = 
               ( DoorListener ) iterator.next();

            // send doorOpened event to this DoorListener
            doorListener.doorOpened(
               new DoorEvent( this, location ) );
         }

         doorLocation = location;

         // declare Thread that ensures automatic Door closing
         Thread closeThread = new Thread( 
            new Runnable() {

               public void run()
               {
                  // close Door if open for more than 3 seconds
                  try {
                     Thread.sleep( AUTOMATIC_CLOSE_DELAY );
                     closeDoor( doorLocation );
                  }

                  // handle exception if interrupted
                  catch ( InterruptedException exception ) {
                     exception.printStackTrace();
                  }                     
               }
            } // end anonymous inner class
         );

         closeThread.start();
      }
      
      // notify all waiting threads that the door has opened
      notifyAll();
      
   } // end method openDoor

   // close Door and send all listeners DoorEvent objects
   public synchronized void closeDoor( Location location )
   {      
      if ( open ) {

         open = false;

         // obtain iterator from Set
         Iterator iterator;
         synchronized( doorListeners )
         {
            iterator = new HashSet( doorListeners ).iterator();
         }

         // get next DoorListener
         while ( iterator.hasNext() ) {
            DoorListener doorListener = 
               ( DoorListener ) iterator.next();

            // send doorClosed event to this DoorListener
            doorListener.doorClosed(
               new DoorEvent( this, location ) );
         }
      }
      
   } // end method closeDoor

   // return whether Door is open or closed
   public synchronized boolean isDoorOpen()
   {
      return open;
   }
}


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 * (C) Copyright 1992-2003 by Deitel & Associates, Inc. and               *
 * Prentice Hall. All Rights Reserved.                                    *
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