code: public static void join(final StringBuilder buf, final String addAtBeginning, final String sep,
              final String addAtEnd, final Iterable<?> iterable) {
          if (!addAtBeginning.isEmpty()) {
              buf.append(addAtBeginning);
          }
          boolean first = true;
          for (final Object item : iterable) {
              if (first) {
                  first = false;
              } else {
                  buf.append(sep);
              }
              buf.append(item.toString());
          }
          if (!addAtEnd.isEmpty()) {
              buf.append(addAtEnd);
          }
      }
docs: A replacement for Java 8's String.join().
  
  @param buf
  The buffer to append to.
  @param addAtBeginning
  The token to add at the beginning of the string.
  @param sep
  The separator string.
  @param addAtEnd
  The token to add at the end of the string.
  @param iterable
  The {@link Iterable} to join.