docs: public static String combineLines( String[] lines,
                                         char separator ) {
          if (lines == null || lines.length == 0) return "";
          StringBuilder sb = new StringBuilder();
          for (int i = 0; i != lines.length; ++i) {
              String line = lines[i];
              if (i != 0) sb.append(separator);
              sb.append(line);
          }
          return sb.toString();
      }