code: public static void appendJSON(Appendable a, JSONValue value) throws IOException {
          if (value == null)
              a.append("null");
          else
              value.appendJSON(a);
      }
docs: Convenience method to append the JSON string for a value to an {@link Appendable}, for
  cases where the value may be {@code null}.
  
  @param   a       the {@link Appendable}
  @param   value   the {@link JSONValue}
  @throws  IOException if thrown by the {@link Appendable}