code: public static void addIfNotNull(JSONWriter writer, String field,
  			Boolean value) throws JSONException {
  		if (value == null)
  			return;
  		writer.key(field);
  		writer.value(value);
  	}
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.