--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/com/go/trove/util/UsageSet.java	Sat Mar 21 11:00:06 2009 +0000
@@ -0,0 +1,107 @@
+/* ====================================================================
+ * 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 that orders its elements based on how recently they have been used.
+ * Most recently used elements appear first in the Set. Elements are marked as
+ * being used whenever they are added to the Set. To re-position an element,
+ * re-add it.
+ *
+ * @author Brian S O'Neill
+ * @version
+ * <!--$$Revision:--> 16 <!-- $-->, <!--$$JustDate:-->  9/07/00 <!-- $-->
+ */
+public class UsageSet extends MapBackedSet {
+    /**
+     * Creates a UsageSet in forward order, MRU first.
+     */
+    public UsageSet() {
+        this(new HashMap());
+    }
+
+    /**
+     * @param backingMap map to use for storage
+     */
+    public UsageSet(Map backingMap) {
+        super(new UsageMap(backingMap));
+    }
+
+    /**
+     * With reverse order, elements are ordered least recently used first. The
+     * ordering of the elements will be consistent with the order they were
+     * added in. Switching to and from reverse order is performed quickly
+     * and is not affected by the current size of the set.
+     */
+    public void setReverseOrder(boolean reverse) {
+        ((UsageMap)mMap).setReverseOrder(reverse);
+    }
+
+    /**
+     * Returns the first element in the set, the most recently used. If reverse
+     * order, then the least recently used is returned.
+     */
+    public Object first() throws NoSuchElementException {
+        return ((UsageMap)mMap).firstKey();
+    }
+
+    /**
+     * Returns the last element in the set, the least recently used. If reverse
+     * order, then the most recently used is returned.
+     */
+    public Object last() throws NoSuchElementException {
+        return ((UsageMap)mMap).lastKey();
+    }
+}