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;
+  }
+
+}

classpath/java/util/Observer.java

@@ -0,0 +1,15 @@
+/* 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 interface Observer {
+  public void update(Observable o, Object arg);
+}

test/Observe.java

@@ -0,0 +1,88 @@
+import java.util.Observer;
+import java.util.Observable;
+
+public class Observe {
+  private static void expect(boolean v) {
+    if (! v) throw new RuntimeException();
+  }
+
+  private static class MyObservable extends Observable {
+    private String value;
+
+    public MyObservable(String value) {
+      this.value = value;
+    }
+
+    public void set(String newValue) {
+      if(!value.equals(newValue)) {
+        value = newValue;
+        setChanged();
+        notifyObservers(value);
+      }
+    }
+  }
+
+  private static class MyObserver implements Observer {
+    private int count = 0;
+    private Observable expectedObs;
+    private Object expectedValue = null;
+    private boolean expected = false;
+
+    public MyObserver(Observable expectedObs) {
+      this.expectedObs = expectedObs;
+    }
+
+    public void update(Observable obs, Object value) {
+      expect(expectedObs == expectedObs);
+      expect(expected);
+      expect(value == expectedValue);
+      expectNothing();
+    }
+
+    public void noUpdate() {
+      expect(!expected);
+    }
+
+    public void expect(Object value) {
+      expected = true;
+      expectedValue = value;
+    }
+
+    public void expectNothing() {
+      expected = false;
+    }
+    
+  }
+
+  public static void main(String[] args) {
+    MyObservable obs = new MyObservable("test");
+    MyObserver o = new MyObserver(obs);
+    MyObserver o2 = new MyObserver(obs);
+
+    obs.set("a");
+
+    obs.addObserver(o);
+    o.expect("b");
+    obs.set("b");
+    o.noUpdate();
+
+    obs.addObserver(o2);
+    o.expect("c");
+    o2.expect("c");
+    obs.set("c");
+    o.noUpdate();
+    o2.noUpdate();
+
+    obs.deleteObserver(o);
+    o.expectNothing();
+    o2.expect("d");
+    obs.set("d");
+    o2.noUpdate();
+
+    obs.deleteObserver(o2);
+    o.expectNothing();
+    o2.expectNothing();
+    obs.set("e");
+
+  }
+}