code: @Nullable
      public DBObject one() {
          DBCursor findOneCursor = copy().limit(-1);
          try {
              return findOneCursor.hasNext() ? findOneCursor.next() : null;
          } finally {
              findOneCursor.close();
          }
      }
docs: Returns the first document that matches the query.
  
  @return the first matching document
  @since 2.12