code: public WriteResult<T, K> update(T query, T object, boolean upsert, boolean multi)
              throws MongoException {
          return update(query, object, upsert, multi, getWriteConcern());
      }
docs: calls {@link DBCollection#update(com.mongodb.DBObject, com.mongodb.DBObject, boolean, boolean, com.mongodb.WriteConcern)} with default WriteConcern.
  
  @param query  search query for old object to update
  @param object object with which to update <tt>q</tt>
  @param upsert if the database should create the element if it does not exist
  @param multi  if the update should be applied to all objects matching (db version 1.1.3 and above)
  See http://www.mongodb.org/display/DOCS/Atomic+Operations
  @return The result
  @throws MongoException If an error occurred