code: private String buildFileName(final String... names) {
          final StringBuilder builder = new StringBuilder();
          for (int i = 0; i < names.length; i++) {
              builder.append(names[i]);
              if (i < names.length - 1) {
                  builder.append(SEPARATOR);
              }
          }
          builder.append(".").append("csv");
          return builder.toString();
      }
docs: Helper method to build suitable fileNames.
  
  @param names different names to be combined
  @return a String for a suitable file name