code: public static String join(String[] strings) {
          StringBuilder builder = new StringBuilder();
          for (int i = 0; i < strings.length; i++) {
              builder.append(strings[i]);
              if (i + 1 < strings.length) builder.append(",");
          }
          return builder.toString();
      }
docs: A simple method for joining an array of strings to a comma seperated string.
  
  @param strings An array of strings.
  @return The array as single string joined by commas