code: private static String joinToString(Iterable<?> iterable, String delimiter) {
          StringBuilder builder = new StringBuilder();
          Iterator<?> iter = iterable.iterator();
          while (iter.hasNext()) {
              builder.append(iter.next());
              if (iter.hasNext()) {
                  builder.append(delimiter);
              }
          }
          return builder.toString();
      }
docs: Concatenate an Iterable<?> set of items with a delimiter between each
  
  @param iterable
  the set of items to concatenate
  @param delimiter
  the character to put between each item
  @return the concatenated string