/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements.  See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License.  You may obtain a copy of the License at *  *      http://www.apache.org/licenses/LICENSE-2.0 *  * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package org.apache.log4j.helpers;import java.util.Hashtable;/**   <code>ThreadLocalMap</code> extends {@link InheritableThreadLocal}   to bequeath a copy of the hashtable of the MDC of the parent   thread.   @author Ceki G&uuml;lc&uuml;   @since 1.2*/final public class ThreadLocalMap extends InheritableThreadLocal {  public  final  Object childValue(Object parentValue) {    Hashtable ht = (Hashtable) parentValue;    if(ht != null) {      return ht.clone();    } else {      return null;    }  }}