code: public static String join(final List<String> strings, final char delimiter) {
          StringBuilder builder = new StringBuilder();
          for (String element : strings) {
              if (builder.length() != 0) {
                  builder.append(delimiter);
              }
              builder.append(element);
          }
          return builder.toString();
      }
docs: Joins strings with the given delimiter
  
  @param strings   the strings to join
  @param delimiter the delimiter
  @return the joined string