--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/com/go/trove/util/MapBackedSet.java	Sat Mar 21 11:00:06 2009 +0000
@@ -0,0 +1,142 @@
+/* ====================================================================
+ * Trove - Copyright (c) 1997-2000 Walt Disney Internet Group
+ * ====================================================================
+ * The Tea Software License, Version 1.1
+ *
+ * Copyright (c) 2000 Walt Disney Internet Group. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. The end-user documentation included with the redistribution,
+ *    if any, must include the following acknowledgment:
+ *       "This product includes software developed by the
+ *        Walt Disney Internet Group (http://opensource.go.com/)."
+ *    Alternately, this acknowledgment may appear in the software itself,
+ *    if and wherever such third-party acknowledgments normally appear.
+ *
+ * 4. The names "Tea", "TeaServlet", "Kettle", "Trove" and "BeanDoc" must
+ *    not be used to endorse or promote products derived from this
+ *    software without prior written permission. For written
+ *    permission, please contact opensource@dig.com.
+ *
+ * 5. Products derived from this software may not be called "Tea",
+ *    "TeaServlet", "Kettle" or "Trove", nor may "Tea", "TeaServlet",
+ *    "Kettle", "Trove" or "BeanDoc" appear in their name, without prior
+ *    written permission of the Walt Disney Internet Group.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED.  IN NO EVENT SHALL THE WALT DISNEY INTERNET GROUP OR ITS
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ * ====================================================================
+ *
+ * For more information about Tea, please see http://opensource.go.com/.
+ */
+
+package com.go.trove.util;
+
+import java.util.*;
+
+/******************************************************************************
+ * A set implementation that is backed by any map.
+ *
+ * @author Brian S O'Neill
+ * @version
+ * <!--$$Revision: 1.1 $-->, <!--$$JustDate:-->  9/07/00 <!-- $-->
+ */
+public class MapBackedSet extends AbstractSet implements java.io.Serializable {
+    // Dummy value to associate with an Object in the backing Map
+    private static final Object PRESENT = new Object();
+
+    protected final Map mMap;
+
+    /**
+     * @param map The map to back this set.
+     */
+    public MapBackedSet(Map map) {
+        mMap = map;
+    }
+
+    /**
+     * Returns an iterator over the elements in this set. The elements
+     * are returned in the order determined by the backing map.
+     *
+     * @return an Iterator over the elements in this set.
+     * @see ConcurrentModificationException
+     */
+    public Iterator iterator() {
+        return mMap.keySet().iterator();
+    }
+
+    /**
+     * Returns the number of elements in this set (its cardinality).
+     *
+     * @return the number of elements in this set (its cardinality).
+     */
+    public int size() {
+        return mMap.size();
+    }
+
+    /**
+     * Returns true if this set contains no elements.
+     *
+     * @return true if this set contains no elements.
+     */
+    public boolean isEmpty() {
+        return mMap.isEmpty();
+    }
+
+    /**
+     * Returns true if this set contains the specified element.
+     *
+     * @return true if this set contains the specified element.
+     */
+    public boolean contains(Object obj) {
+        return mMap.containsKey(obj);
+    }
+
+    /**
+     * Adds the specified element to this set if it is not already
+     * present.
+     *
+     * @param obj element to be added to this set.
+     * @return true if the set did not already contain the specified element.
+     */
+    public boolean add(Object obj) {
+        return mMap.put(obj, PRESENT) == null;
+    }
+
+    /**
+     * Removes the given element from this set if it is present.
+     *
+     * @param obj object to be removed from this set, if present.
+     * @return true if the set contained the specified element.
+     */
+    public boolean remove(Object obj) {
+        return mMap.remove(obj) == PRESENT;
+    }
+
+    /**
+     * Removes all of the elements from this set.
+     */
+    public void clear() {
+        mMap.clear();
+    }
+}