code: public static List<String> extractNonExistingColumns(final Collection<String> expectedColumns,
          final Collection<String> actualColumns) {
          final List<String> columnsNotSpecifiedInExpectedDataSet = new ArrayList<String>();
  
          for (String column : expectedColumns) {
              if (!actualColumns.contains(column.toLowerCase())) {
                  columnsNotSpecifiedInExpectedDataSet.add(column.toLowerCase());
              }
          }
  
          return columnsNotSpecifiedInExpectedDataSet;
      }
docs: Provides list of columns defined in expectedColumns, but not listed in actualColumns.