code: @SuppressWarnings("unchecked")
      public QueryBuilder withinBox(final double x, final double y, final double x2, final double y2) {
          addOperand(QueryOperators.WITHIN,
                     new BasicDBObject(QueryOperators.BOX, new Object[]{new Double[]{x, y}, new Double[]{x2, y2}}));
          return this;
      }
docs: Equivalent to a $within operand, based on a bounding box using represented by two corners
  
  @param x  the x coordinate of the first box corner.
  @param y  the y coordinate of the first box corner.
  @param x2 the x coordinate of the second box corner.
  @param y2 the y coordinate of the second box corner.
  @return {@code this}