code: private double calcEntropy(final List<Match> matches, final boolean include_brute_force)
      {
          double entropy = 0;
          for (Match match : matches)
          {
              if (include_brute_force || !(match instanceof BruteForceMatch))
              {
                  entropy += match.calculateEntropy();
              }
          }
          return entropy;
      }
docs: Helper method to calculate entropy from a list of matches.
  
  @param matches the list of matches
  @return the sum of the entropy in the list passed in