diff -u -r org.orig/apache/commons/lang/enums/Enum.java org/apache/commons/lang/enums/Enum.java
--- org.orig/apache/commons/lang/enums/Enum.java	2007-02-09 22:16:48.000000000 -0600
+++ org/apache/commons/lang/enums/Enum.java	2007-07-27 10:00:21.000000000 -0500
@@ -302,7 +302,12 @@
     /**
      * <code>Map</code>, key of class name, value of <code>Entry</code>.
      */
-    private static final Map cEnumClasses = new WeakHashMap();
+    private static Map cEnumClasses 
+        //Bug 334: To avoid exposing a mutating map,
+        //we copy it each time we add to it. This is cheaper than
+        //using a synchronized map since we are almost entirely reads
+        //TODO: should this  be valatile?
+        = new WeakHashMap();
     
     /**
      * The string representation of the Enum.
@@ -395,18 +400,23 @@
         if (ok == false) {
             throw new IllegalArgumentException("getEnumClass() must return a superclass of this class");
         }
-        
-        // create entry
-        Entry entry = (Entry) cEnumClasses.get(enumClass);
-        if (entry == null) {
-            entry = createEntry(enumClass);
-            cEnumClasses.put(enumClass, entry);
+        Entry entry;
+        synchronized( Enum.class ) { //Bug 334
+            // create entry
+            entry = (Entry) cEnumClasses.get(enumClass);
+            if (entry == null) {
+                entry = createEntry(enumClass);
+                Map myMap = new WeakHashMap( cEnumClasses );
+                myMap.put(enumClass, entry);
+                cEnumClasses = myMap;
+            }
         }
         if (entry.map.containsKey(name)) {
             throw new IllegalArgumentException("The Enum name must be unique, '" + name + "' has already been added");
         }
         entry.map.put(name, this);
         entry.list.add(this);
+        
     }
 
     /**