code: public static String join(List<String> parts, String separator) {
  		Iterator<String> it = parts.iterator();
  		StringBuilder builder = new StringBuilder();
  		while (it.hasNext()) {
  			String part = it.next();
  			builder.append(part);
  			if (it.hasNext()) {
  				builder.append(separator);
  			}
  		}
  		return builder.toString();
  	}
docs: Joins a list of strings using the specified separator.
  
  @param parts string parts
  @param separator separator
  @return concatenated string