code: public static String join(String[] array, String separator) {
          int len = array.length;
          if (len == 0) return "";
  
          StringBuilder out = new StringBuilder();
          out.append(array[0]);
          for (int i = 1; i < len; i++) {
              out.append(separator).append(array[i]);
          }
          return out.toString();
      }
docs: Join an array of strings with the given separator.
  <p>
  Note: This might be replaced by utility method from commons-lang or guava someday
  if one of those libraries is added as dependency.
  </p>
  
  @param array     The array of strings
  @param separator The separator
  @return the resulting string