code: public static Boolean parserBoolean(JsonPullParser parser) throws IOException,
  			JsonFormatException {
  
  		State eventType = parser.getEventType();
  		if (eventType == State.VALUE_NULL) {
  			return null;
  		} else if (eventType == State.VALUE_BOOLEAN) {
  			return parser.getValueBoolean();
  		} else {
  			throw new IllegalStateException("unexpected state. expected=VALUE_BOOLEAN, but get="
  					+ eventType.toString());
  		}
  	}
docs: Parses the current token as a boolean.
  @param parser
  @return {@link Boolean}
  @throws IOException
  @throws JsonFormatException
  @author vvakame