implement java/util/Observ*

classpath/java/util/Observable.java

@@ -0,0 +1,73 @@
+/* Copyright (c) 2008-2013, Avian Contributors
+
+   Permission to use, copy, modify, and/or distribute this software
+   for any purpose with or without fee is hereby granted, provided
+   that the above copyright notice and this permission notice appear
+   in all copies.
+
+   There is NO WARRANTY for this software.  See license.txt for
+   details. */
+
+package java.util;
+
+public class Observable {
+
+  private List<Observer> observers = new ArrayList<Observer>();
+  private boolean changed = false;
+
+  public void addObserver(Observer o) {
+    if(o == null) {
+      throw new NullPointerException();
+    }
+    synchronized(this) {
+      if(!observers.contains(o)) {
+        observers.add(o);
+      }
+    }
+  }
+
+  public synchronized int countObservers() {
+    return observers.size();
+  }
+
+  public void deleteObserver(Observer o) {
+    if(o == null) {
+      throw new NullPointerException();
+    }
+    synchronized(this) {
+      observers.remove(o);
+    }
+  }
+
+  public void notifyObservers() {
+    notifyObservers(null);
+  }
+
+  public synchronized void notifyObservers(Object value) {
+    Observer[] obsArray = null;
+    synchronized(this) {
+      if(hasChanged()) {
+        clearChanged();
+        obsArray = observers.toArray(new Observer[observers.size()]);
+      }
+    }
+    if(obsArray != null) {
+      for(Observer obs : obsArray) {
+        obs.update(this, value);
+      }
+    }
+  }
+
+  public boolean hasChanged() {
+    return changed;
+  }
+
+  protected void setChanged() {
+    changed = true;
+  }
+
+  protected void clearChanged() {
+    changed = false;
+  }
+
+}