--- old/src/share/classes/com/sun/jndi/toolkit/url/GenericURLContext.java	Mon May 13 06:49:21 2013
+++ new/src/share/classes/com/sun/jndi/toolkit/url/GenericURLContext.java	Mon May 13 06:49:19 2013
@@ -53,7 +53,8 @@
     @SuppressWarnings("unchecked") // Expect Hashtable<String, Object>
     public GenericURLContext(Hashtable<?,?> env) {
         // context that is not tied to any specific URL
-        myEnv = (Hashtable<String, Object>)env;  // copied on write
+        myEnv =
+            (Hashtable<String, Object>)(env == null ? null : env.clone());
     }
 
     public void close() throws NamingException {
@@ -494,7 +495,6 @@
             if (myEnv == null) {
                 return null;
             }
-            myEnv = (Hashtable<String, Object>)myEnv.clone();
             return myEnv.remove(propName);
     }
 
@@ -501,9 +501,9 @@
     @SuppressWarnings("unchecked") // clone()
     public Object addToEnvironment(String propName, Object propVal)
         throws NamingException {
-            myEnv = (myEnv == null)
-                    ? new Hashtable<String, Object>(11, 0.75f)
-                    : (Hashtable<String, Object>)myEnv.clone();
+            if (myEnv == null) {
+                myEnv = new Hashtable<String, Object>(11, 0.75f);
+            }
             return myEnv.put(propName, propVal);
     }