code: public static Double parserDouble(JsonPullParser parser) throws IOException,
  			JsonFormatException {
  
  		State eventType = parser.getEventType();
  		if (eventType == State.VALUE_NULL) {
  			return null;
  		} else if (eventType == State.VALUE_DOUBLE) {
  			return parser.getValueDouble();
  		} else {
  			throw new IllegalStateException("unexpected state. expected=VALUE_DOUBLE, but get="
  					+ eventType.toString());
  		}
  	}
docs: Parses the current token as a double-precision floating point value.
  @param parser
  @return {@link Double}
  @throws IOException
  @throws JsonFormatException
  @author vvakame