@Override
    public int hashCode() {
        final int prime = 31;
        int result = super.hashCode();
        result = prime * result + type;
        return result;
    }
RollingCalendar is a helper class to DailyRollingFileAppender. Given a
periodicity type and the current time, it computes the start of the next
interval.
metamorphosis-client-extension/src/main/java/com/taobao/metamorphosis/client/extension/log4j/DailyRollingFileStreamAppender.java