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Java > Open Source Codes > edu > rice > cs > drjava > model > EventNotifier


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33
34 package edu.rice.cs.drjava.model;
35
36 import java.util.LinkedList JavaDoc;
37 import edu.rice.cs.util.ReaderWriterLock;
38 import edu.rice.cs.util.swing.Utilities;
39
40 /** Base class for all component-specific EventNotifiers. This class provides common methods to
41  * manage listeners of a specific type. T the type of the listener class to be managed.
42  * @version $Id: EventNotifier.java 3901 2006-06-30 05:28:11Z rcartwright $
43  */
44 public abstract class EventNotifier<T> {
45
46   /** All T Listeners that are listening to the model. Accesses to this collection are protected by the
47    * ReaderWriterLock. The collection must be synchronized, since multiple readers could access it at once.
48    */
49   protected final LinkedList JavaDoc<T> _listeners = new LinkedList JavaDoc<T>();
50
51   /** Provides synchronization primitives for solving the readers/writers problem. In EventNotifier, adding and
52    * removing listeners are considered write operations, and all notifications are considered read operations. Multiple
53    * reads can occur simultaneously, but only one write can occur at a time, and no reads can occur during a write.
54    */
55   protected final ReaderWriterLock _lock = new ReaderWriterLock();
56
57   /** Adds a listener to the notifier.
58    * @param listener a listener that reacts on events
59    */
60   public void addListener(T listener) {
61 // Utilities.showDebug("Adding listener " + listener + " to event notifier " + this);
62 _lock.startWrite();
63     try { _listeners.add(listener); }
64     finally {
65       _lock.endWrite();
66 // new ScrollableDialog(null, "Released writeLock on event queue", "", "").show();
67 }
68   }
69
70   /** Removes a listener from the notifier.
71    * @param listener a listener that reacts on events
72    */
73   public void removeListener(T listener) {
74 // Utilities.show("writeLock on _listeners grabbed by " + this);
75 _lock.startWrite();
76     try { _listeners.remove(listener); }
77     finally {
78       _lock.endWrite();
79 // new ScrollableDialog(null, "Released writeLock on event queue", "", "").show();
80 }
81   }
82
83   /** Removes all listeners from this notifier. */
84   public void removeAllListeners() {
85 // new ScrollableDialog(null, "Grabbing writeLock on event queue", "", "").show();
86 _lock.startWrite();
87     try { _listeners.clear(); }
88     finally {
89       _lock.endWrite();
90 // new ScrollableDialog(null, "Released writeLock on event queue", "", "").show();
91 }
92   }
93 }
94
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