--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/visualizer/Data/src/com/sun/hotspot/igv/data/Event.java	Tue Feb 07 22:41:09 2012 +0100
@@ -0,0 +1,87 @@
+/*
+ * Copyright (c) 2008, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+package com.sun.hotspot.igv.data;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ *
+ * @author Thomas Wuerthinger
+ */
+public abstract class Event<L> {
+
+    private List<L> listener;
+    private boolean fireEvents;
+    private boolean eventWasFired;
+    
+    public Event() {
+        listener = new ArrayList<>();
+        fireEvents = true;
+    }
+
+    public void addListener(L l) {
+        listener.add(l);
+    }
+
+    public void addListenerAndFire(L l) {
+        addListener(l);
+        fire(l);
+    }
+
+    /**
+     * Remove listener
+     * @param l
+     */
+    public void removeListener(final L l) {
+        listener.remove(l);
+    }
+
+    public void fire() {
+        if(fireEvents) {
+            List<L> tmpList = new ArrayList<>(listener);
+            for (L l : tmpList) {
+                fire(l);
+            }
+        } else {
+            eventWasFired = true;
+        }
+    }
+
+    public void beginAtomic() {
+        assert fireEvents : "endAtomic has to be called before another beginAtomic may be called";
+        this.fireEvents = false;
+        this.eventWasFired = false;
+    }
+
+    public void endAtomic() {
+        assert !fireEvents : "beginAtomic has to be called first";
+        this.fireEvents = true;
+        if(eventWasFired) {
+            fire();
+        }
+    }
+    
+    protected abstract void fire(L l);
+}