public static long getLastDay4Month(int year, int month) {
        long lastDay = 0L;
        Calendar cal = Calendar.getInstance();
        cal.set(Calendar.YEAR, year);
        cal.set(Calendar.MONTH, month);
        //1 represents a zero next month, can be seen as the end of the first day of the month most one day, but the data table on the last day of the zero point on the line
        cal.set(Calendar.DAY_OF_MONTH, 0);
        cal.set(Calendar.HOUR_OF_DAY, 0);
        cal.set(Calendar.MINUTE, 0);
        cal.set(Calendar.SECOND, 0);
        cal.set(Calendar.MILLISECOND, 0);
        lastDay = cal.getTimeInMillis() / 1000L;
        return lastDay;
    }
@author yumo.lck
@param year
@param month
@return
core/src/main/java/com/dtstack/flink/sql/util/DateUtil.java