code: public static void addData(final Crosstab<Number> mainCrosstab, final Crosstab<Number> partialCrosstab,
              final CrosstabDimension columnDimension, final CrosstabDimension measureDimension) {
          if (partialCrosstab != null) {
  
              final CrosstabNavigator<Number> mainNavigator = new CrosstabNavigator<>(mainCrosstab);
              final CrosstabNavigator<Number> nav = new CrosstabNavigator<>(partialCrosstab);
  
              for (final String columnCategory : columnDimension.getCategories()) {
                  // just navigate through the dimensions because is the column
                  // dimension
                  nav.where(columnDimension, columnCategory);
                  mainNavigator.where(columnDimension, columnCategory);
                  // navigate and sum up data
                  final List<String> categories = measureDimension.getCategories();
                  for (final String measureCategory : categories) {
                      sumUpData(mainNavigator, nav, measureDimension, measureCategory);
                  }
              }
          }
      }
docs: Add the values of partial crosstab to the main crosstab
  
  @param mainCrosstab
  - main crosstab
  @param partialCrosstab
  - partial crosstab