public void getTimes(Properties props) throws Exception {
        String valueString;
        int value;

        valueString = props.getProperty("interval");
        if (valueString == null) {
            throw new MissingPropertiesException("monitor interval");
        }
        value = Integer.parseInt(valueString);

        if (value <= 0) {
            throw new MissingPropertiesException("monitor interval > 0");
        }
        checkInterval = value;

        valueString = props.getProperty("duration");
        if (valueString == null) {
            throw new MissingPropertiesException("duration");
        }
        value = Integer.parseInt(valueString);
        if (value <= 0) {
            throw new MissingPropertiesException("duration > 0");
        }
        if ((value % checkInterval) != 0) {
            throw new MissingPropertiesException("duration % checkInterval");
        }
        monitorTime = value;

        valueString = props.getProperty("departure");
        if (valueString == null) {
            throw new MissingPropertiesException("departure offset");
        }
        value = Integer.parseInt(valueString);
        if (value <= 0) {
            throw new MissingPropertiesException("departure > 0");
        }
        if ((value % checkInterval) != 0) {
            throw new MissingPropertiesException("departure % checkInterval");
        }
        departureOffset = value;
    }