code: private void add2MBR(int[] entrySorting, double[] ub, double[] lb, int index) {
      SpatialComparable currMBR = node.getEntry(entrySorting[index]);
      for(int d = 0; d < currMBR.getDimensionality(); d++) {
        double max = currMBR.getMax(d);
        if(max > ub[d]) {
          ub[d] = max;
        }
        double min = currMBR.getMin(d);
        if(min < lb[d]) {
          lb[d] = min;
        }
      }
    }
docs: Adds the minimum and maximum bounds of the MBR of entry number
  <code>entrySorting[index]</code> to the dimension-wise
  upper and lower bounds, <code>ub</code> and <code>lb</code>. Note that if
  this method is called for <code>ub</code> and <code>lb</code> which are
  already owned by an MBR, this update operation also updates the MBR defined
  by those bounds.
  
  @param entrySorting a sorting providing the mapping of <code>index</code>
  to the entry to be added
  @param ub the upper bound of the MBR to be extended
  @param lb the lower bound of the MBR to be extended
  @param index the index in the sorting referencing the entry to be added