docs: public static String joinP(String delimiter, char... chars) {
          StringBuilder builder = new StringBuilder(chars.length + (delimiter.length() * chars.length));
          boolean first = true;
          for (char c : chars) {
              if (first) {
                  first = false;
              } else {
                  builder.append(delimiter);
              }
              builder.append(c);
          }
          return builder.toString();
      }