--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/code/observer-example.java	Fri Aug 10 22:15:51 2007 +0200
@@ -0,0 +1,31 @@
+        import java.util.Observable;
+        import java.util.Observer;
+
+        public class MessageBoard extends Observable {
+          private String message;
+
+          public String getMessage() {
+            return message;
+          }
+
+          public void changeMessage(String message) {
+            this.message = message;
+            setChanged();
+            notifyObservers(message);
+          }
+
+          public static void main(String[] args) {
+            MessageBoard board = new MessageBoard();
+            Student bob = new Student();
+            Student joe = new Student();
+            board.addObserver(bob);
+            board.addObserver(joe);
+            board.changeMessage("More Homework!");
+          }
+        }
+
+        class Student implements Observer {
+          public void update(Observable o, Object arg) {
+            System.out.println("Message board changed: " + arg);
+          }
+        }