--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/java/io/ExpiringCache.java	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,127 @@
+/*
+ * Copyright 2002-2004 Sun Microsystems, Inc.  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.  Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun in the LICENSE file that accompanied this code.
+ *
+ * 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+/*
+ */
+
+package java.io;
+
+import java.util.Iterator;
+import java.util.Map;
+import java.util.LinkedHashMap;
+import java.util.Set;
+
+class ExpiringCache {
+    private long millisUntilExpiration;
+    private Map  map;
+    // Clear out old entries every few queries
+    private int queryCount;
+    private int queryOverflow = 300;
+    private int MAX_ENTRIES = 200;
+
+    static class Entry {
+        private long   timestamp;
+        private String val;
+
+        Entry(long timestamp, String val) {
+            this.timestamp = timestamp;
+            this.val = val;
+        }
+
+        long   timestamp()                  { return timestamp;           }
+        void   setTimestamp(long timestamp) { this.timestamp = timestamp; }
+
+        String val()                        { return val;                 }
+        void   setVal(String val)           { this.val = val;             }
+    }
+
+    ExpiringCache() {
+        this(30000);
+    }
+
+    ExpiringCache(long millisUntilExpiration) {
+        this.millisUntilExpiration = millisUntilExpiration;
+        map = new LinkedHashMap() {
+            protected boolean removeEldestEntry(Map.Entry eldest) {
+              return size() > MAX_ENTRIES;
+            }
+          };
+    }
+
+    synchronized String get(String key) {
+        if (++queryCount >= queryOverflow) {
+            cleanup();
+        }
+        Entry entry = entryFor(key);
+        if (entry != null) {
+            return entry.val();
+        }
+        return null;
+    }
+
+    synchronized void put(String key, String val) {
+        if (++queryCount >= queryOverflow) {
+            cleanup();
+        }
+        Entry entry = entryFor(key);
+        if (entry != null) {
+            entry.setTimestamp(System.currentTimeMillis());
+            entry.setVal(val);
+        } else {
+            map.put(key, new Entry(System.currentTimeMillis(), val));
+        }
+    }
+
+    synchronized void clear() {
+        map.clear();
+    }
+
+    private Entry entryFor(String key) {
+        Entry entry = (Entry) map.get(key);
+        if (entry != null) {
+            long delta = System.currentTimeMillis() - entry.timestamp();
+            if (delta < 0 || delta >= millisUntilExpiration) {
+                map.remove(key);
+                entry = null;
+            }
+        }
+        return entry;
+    }
+
+    private void cleanup() {
+        Set keySet = map.keySet();
+        // Avoid ConcurrentModificationExceptions
+        String[] keys = new String[keySet.size()];
+        int i = 0;
+        for (Iterator iter = keySet.iterator(); iter.hasNext(); ) {
+            String key = (String) iter.next();
+            keys[i++] = key;
+        }
+        for (int j = 0; j < keys.length; j++) {
+            entryFor(keys[j]);
+        }
+        queryCount = 0;
+    }
+}