code: public static void addIfNotNullShort(JSONWriter writer, String field,
  			Date value) throws JSONException {
  		final SimpleDateFormat format = RedmineDateUtils.SHORT_DATE_FORMAT
  				.get();
  		JsonOutput.addIfNotNull(writer, field, value, format);
  	}
docs: Adds a value to a writer if value is not <code>null</code>.
  
  @param writer
  writer to add object to.
  @param field
  field name to set.
  @param value
  field value.
  @throws JSONException
  if io error occurs.