--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/org/eclipse/jetty/util/ConcurrentHashSet.java	Wed Sep 07 21:15:48 2016 -0600
@@ -0,0 +1,126 @@
+//
+//  ========================================================================
+//  Copyright (c) 1995-2014 Mort Bay Consulting Pty. Ltd.
+//  ------------------------------------------------------------------------
+//  All rights reserved. This program and the accompanying materials
+//  are made available under the terms of the Eclipse Public License v1.0
+//  and Apache License v2.0 which accompanies this distribution.
+//
+//      The Eclipse Public License is available at
+//      http://www.eclipse.org/legal/epl-v10.html
+//
+//      The Apache License v2.0 is available at
+//      http://www.opensource.org/licenses/apache2.0.php
+//
+//  You may elect to redistribute this code under either of these licenses.
+//  ========================================================================
+//
+
+package org.eclipse.jetty.util;
+
+import java.util.AbstractSet;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+
+public class ConcurrentHashSet<E> extends AbstractSet<E> implements Set<E>
+{
+    private final Map<E, Boolean> _map = new ConcurrentHashMap<E, Boolean>();
+    private transient Set<E> _keys = _map.keySet();
+
+    public ConcurrentHashSet()
+    {
+    }
+
+    @Override
+    public boolean add(E e)
+    {
+        return _map.put(e,Boolean.TRUE) == null;
+    }
+
+    @Override
+    public void clear()
+    {
+        _map.clear();
+    }
+
+    @Override
+    public boolean contains(Object o)
+    {
+        return _map.containsKey(o);
+    }
+
+    @Override
+    public boolean containsAll(Collection<?> c)
+    {
+        return _keys.containsAll(c);
+    }
+
+    @Override
+    public boolean equals(Object o)
+    {
+        return o == this || _keys.equals(o);
+    }
+
+    @Override
+    public int hashCode()
+    {
+        return _keys.hashCode();
+    }
+
+    @Override
+    public boolean isEmpty()
+    {
+        return _map.isEmpty();
+    }
+
+    @Override
+    public Iterator<E> iterator()
+    {
+        return _keys.iterator();
+    }
+
+    @Override
+    public boolean remove(Object o)
+    {
+        return _map.remove(o) != null;
+    }
+
+    @Override
+    public boolean removeAll(Collection<?> c)
+    {
+        return _keys.removeAll(c);
+    }
+
+    @Override
+    public boolean retainAll(Collection<?> c)
+    {
+        return _keys.retainAll(c);
+    }
+
+    @Override
+    public int size()
+    {
+        return _map.size();
+    }
+
+    @Override
+    public Object[] toArray()
+    {
+        return _keys.toArray();
+    }
+
+    @Override
+    public <T> T[] toArray(T[] a)
+    {
+        return _keys.toArray(a);
+    }
+
+    @Override
+    public String toString()
+    {
+        return _keys.toString();
+    }
+}