public class LinkedHashMap<K,V> extends 
  HashMap<K,V> implements Map<K,V>{
  
  static class Entry<K,V> 
    extends HashMap.Node<K,V> {
      Entry<K,V> before, after;
      Entry(int hash, K key, V value, Node<K,V> next) {
        super(hash, key, value, next);
      }
  }
  
   /**
   * The head (eldest) of the doubly linked list.
   */
   transient LinkedHashMap.Entry<K,V> head;

   /**
   * The tail (youngest) of the doubly linked list.
   */
   transient LinkedHashMap.Entry<K,V> tail;
  .....
}