LocalDateTime

@Component
public class DateUtil {

    public final static String EMPTY_SRING = "";
    public final static String DEFAULT_PATTERN = "yyyy-MM-dd HH:mm:ss";
    public final static long DATE_TIME = 1000 * 24 * 60 * 60;
    public final static long HOUR_TIME = 1000 * 60 * 60;
    public final static long MINUTE_TIME = 1000 * 60;
    public LocalDateTime parseDate(String timeStr) {
//        return new LocalDateTimeStringConverter().fromString(timeStr);
        DateTimeFormatter pattern =
                DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");

        //严格按照ISO yyyy-MM-dd验证，03写成3都不行
        return LocalDateTime.parse(timeStr, pattern);
    }

    public String currentDateDay() {
        LocalDate ldt = LocalDate.now();
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
        return ldt.format(formatter);
    }

    public String currentDateTime() {
        LocalDateTime ldt = LocalDateTime.now();
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        return ldt.format(formatter);
    }

    public String afterCurrentDate(LocalDateTime dt, int mount, int unit) {
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        LocalDateTime ldt = LocalDateTime.now();
        if (dt != null) {
            ldt = dt;
        }
        if (unit == ConstUtil.UNIT_SECOND) {
            return ldt.plusSeconds(mount).format(formatter);
        } else if (unit == ConstUtil.UNIT_MINUTE) {
            return ldt.plusMinutes(mount).format(formatter);
        } else if (unit == ConstUtil.UNIT_HOUR) {
            return ldt.plusHours(mount).format(formatter);
        } else if (unit == ConstUtil.UNIT_DAY) {
            return ldt.plusDays(mount).format(formatter);
        } else if (unit == ConstUtil.UNIT_WEEK) {
            return ldt.plusWeeks(mount).format(formatter);
        } else if (unit == ConstUtil.UNIT_MONTH) {
            return ldt.plusMonths(mount).format(formatter);
        } else if (unit == ConstUtil.UNIT_YEAR) {
            return ldt.plusYears(mount).format(formatter);
        }
        return ldt.format(formatter);
    }

    public String beforeCurrentDate(LocalDateTime dt, int mount, int unit) {
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        LocalDateTime ldt = LocalDateTime.now();
        if (dt != null) {
            ldt = dt;
        }
        if (unit == ConstUtil.UNIT_SECOND) {
            return ldt.minusSeconds(mount).format(formatter);
        } else if (unit == ConstUtil.UNIT_MINUTE) {
            return ldt.minusMinutes(mount).format(formatter);
        } else if (unit == ConstUtil.UNIT_HOUR) {
            return ldt.minusHours(mount).format(formatter);
        } else if (unit == ConstUtil.UNIT_DAY) {
            return ldt.minusDays(mount).format(formatter);
        } else if (unit == ConstUtil.UNIT_WEEK) {
            return ldt.minusWeeks(mount).format(formatter);
        } else if (unit == ConstUtil.UNIT_MONTH) {
            return ldt.minusMonths(mount).format(formatter);
        } else if (unit == ConstUtil.UNIT_YEAR) {
            return ldt.minusYears(mount).format(formatter);
        }
        return ldt.format(formatter);
    }

    /**
     * @param date
     * @return Date
     */
    public static Date convertStringToDate(String date) {
        try {
            return new SimpleDateFormat(DEFAULT_PATTERN).parse(date);
        } catch (ParseException e) {
            return null;
        }
    }

    /**
     * 把日期转换成yyyy-MM-dd HH:mm:ss格式
     *
     * @param date
     * @return String
     */
    public static String convertDate(Date date) {
        if (date == null) {
            return EMPTY_SRING;
        }
        return new SimpleDateFormat(DEFAULT_PATTERN).format(date);
    }
    /**
     * 把时间加上day天后返回，如果传负数代表减day天
     *
     * @param date
     * @param day
     * @return Date
     */
    public static Date dateAdd(Date date, int day) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        calendar.set(Calendar.DATE, calendar.get(Calendar.DATE) + day);
        return calendar.getTime();
    }
}

 

来源：https://www.cnblogs.com/yoyotl/p/11734531.html