content: /*
   * Copyright 1999-2012 Alibaba Group.
   *  
   * Licensed 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 com.alibaba.cobar.config.util;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map.Entry;
  import java.util.Set;
  
  public class OrderRetainingMap<K, V> extends HashMap<K, V> {
      private static final long serialVersionUID = 1L;
  
      private Set<K> keyOrder = new ArraySet<K>();
      private List<V> valueOrder = new ArrayList<V>();
  
      @Override
      public V put(K key, V value) {
          keyOrder.add(key);
          valueOrder.add(value);
          return super.put(key, value);
      }
  
      @Override
      public Collection<V> values() {
          return Collections.unmodifiableList(valueOrder);
      }
  
      @Override
      public Set<K> keySet() {
          return Collections.unmodifiableSet(keyOrder);
      }
  
      @Override
      public Set<Entry<K, V>> entrySet() {
          throw new UnsupportedOperationException();
      }
  
      private static class ArraySet<T> extends ArrayList<T> implements Set<T> {
  
          private static final long serialVersionUID = 1L;
      }
  
  }
  