/** Removes this entry from the linked list. */
 private void remove() {
   prev.next = next;
   next.prev = prev;
   prev = null;
   next = null;
 }
 /** Inserts this entry before the specified existing entry in the list. */
 private void addBefore(ChainedEntry existingEntry) {
   next = existingEntry;
   prev = existingEntry.prev;
   prev.next = this;
   next.prev = this;
 }
 private ChainedEntry initEntryChain() {
   ChainedEntry header = new ChainedEntry(-1, -1, null);
   header.prev = header.next = header;
   return header;
 }