Initial revision

From-SVN: r26263

libjava/java/util/Observable.java

@@ -0,0 +1,98 @@
+/* Copyright (C) 1998, 1999  Cygnus Solutions
+
+   This file is part of libgcj.
+
+This software is copyrighted work licensed under the terms of the
+Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
+details.  */
+
+package java.util;
+ 
+/**
+ * @author Warren Levy <warrenl@cygnus.com>
+ * @date September 2, 1998.
+ */
+/* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
+ * "The Java Language Specification", ISBN 0-201-63451-1
+ * plus online API docs for JDK 1.2 beta from http://www.javasoft.com.
+ * Status:  Believed complete and correct.
+ */
+ 
+public class Observable
+{
+  /* tracks whether this object has changed */
+  private boolean changed;
+
+  /* list of the Observers registered as interested in this Observable */
+  private Vector observerVec;
+
+  /* TBD: This might be better implemented as an Observer[]
+   * but that would mean writing more code rather than making use of
+   * the existing Vector class (this also implies a larger text code
+   * space in resulting executables).  The tradeoff is one of speed
+   * (manipulating the Observer[] directly) vs. size/reuse.  In the future,
+   * we may decide to make the tradeoff and reimplement with an Observer[].
+   */
+
+  public Observable()
+  {
+    changed = false;
+    observerVec = new Vector();
+  }
+
+  public synchronized void addObserver(Observer obs)
+  {
+    // JDK 1.2 spec says not to add this if it is already there
+    if (!observerVec.contains(obs))
+      observerVec.addElement(obs);
+  }
+
+  protected synchronized void clearChanged()
+  {
+    changed = false;
+  }
+
+  public synchronized int countObservers()
+  {
+    return observerVec.size();
+  }
+
+  public synchronized void deleteObserver(Observer obs)
+  {
+    observerVec.removeElement(obs);
+  }
+
+  public synchronized void deleteObservers()
+  {
+    observerVec.removeAllElements();
+  }
+
+  public synchronized boolean hasChanged()
+  {
+    return changed;
+  }
+
+  public void notifyObservers()
+  {
+    notifyObservers(null);
+  }
+
+  public void notifyObservers(Object arg)
+  {
+    if (changed)
+      {
+	/* The JDK 1.2 spec states that though the order of notification
+	 * is unspecified in subclasses, in Observable it is in the order
+	 * of registration.
+	 */
+        for (int i = 0, numObs = observerVec.size(); i < numObs; i++)
+          ((Observer) (observerVec.elementAt(i))).update(this, arg);
+        changed = false;
+      }
+  }
+
+  protected synchronized void setChanged()
+  {
+    changed = true;
+  }
+}