code: public Object remove(Object key) throws ObjectManagerException {
          Entry node = find(key);
          if (node == null)
              return null;
          Object result = node.value;
          rbDelete(node);
          return result;
      }
docs: Removes a mapping with the specified key from this TreeMap.
  
  @param key the key of the mapping to remove
  
  @return the value of the removed mapping or null if key is not a key in
  this TreeMap
  
  @exception ClassCastException
  when the key cannot be compared with the keys in this
  TreeMap
  @exception NullPointerException
  when the key is null and the comparator cannot handle null
  @throws ObjectManagerException