时间工具类

import java.time.*;
import java.time.format.DateTimeFormatter;
import java.util.Date;

public class TimeUtil {
    /**
     * 北京时间
     */
    private static final ZoneOffset BEIJING_ZONE = ZoneOffset.of("+8");

    /**
     * 标准日期时间格式，精确到秒：yyyy-MM-dd HH:mm:ss
     */
    private static final String NORM_DATETIME_PATTERN = "yyyy-MM-dd HH:mm:ss";
    /**
     * 标准日期格式：yyyy-MM-dd
     */
    private static final String NORM_DATE_PATTERN = "yyyy-MM-dd";

    /**
     * 转换成时间戳
     *
     * @param localDateTime 当前日期时间
     * @return 时间戳
     */
    public static Long toTimestamp(LocalDateTime localDateTime) {
        if (localDateTime == null) {
            return null;
        }

        return localDateTime.toEpochSecond(BEIJING_ZONE);
    }

    /**
     * 转换成时间戳
     *
     * @param localDate 当前日期
     * @return 时间戳
     */
    public static Long toTimestamp(LocalDate localDate) {
        if (localDate == null) {
            return null;
        }

        return localDate.atStartOfDay(BEIJING_ZONE).toEpochSecond();
    }

    /**
     * 转换成Date
     *
     * @param localDateTime 当前日期时间
     * @return Date日期
     */
    public static Date toDate(LocalDateTime localDateTime) {
        if (localDateTime == null) {
            return null;
        }

        ZonedDateTime zonedDateTime = localDateTime.atZone(BEIJING_ZONE);
        Instant instant = zonedDateTime.toInstant();
        return Date.from(instant);
    }

    /**
     * 转换成Date
     *
     * @param localDate 当前日期
     * @return Date日期
     */
    public static Date toDate(LocalDate localDate) {
        if (localDate == null) {
            return null;
        }

        ZonedDateTime zonedDateTime = localDate.atStartOfDay(BEIJING_ZONE);
        Instant instant = zonedDateTime.toInstant();
        return Date.from(instant);
    }

    /**
     * 转换成时间字符串
     *
     * @param localDateTime 当前日期时间
     * @return 时间字符串
     */
    public static String toString(LocalDateTime localDateTime) {
        if (localDateTime == null) {
            return null;
        }

        return localDateTime.format(DateTimeFormatter.ofPattern(NORM_DATETIME_PATTERN));
    }

    /**
     * 转换成时间字符串
     *
     * @param localDate 当前日期
     * @return 时间字符串
     */
    public static String toString(LocalDate localDate) {
        if (localDate == null) {
            return null;
        }

        return localDate.format(DateTimeFormatter.ofPattern(NORM_DATE_PATTERN));
    }

    /**
     * 转换成日期时间
     *
     * @param text 时间字符串
     * @return 日期时间
     */
    public static LocalDateTime parseLocalDateTime(CharSequence text) {
        if (text == null) {
            return null;
        }

        return LocalDateTime.parse(text, DateTimeFormatter.ofPattern(NORM_DATETIME_PATTERN));
    }

    /**
     * 转换成日期
     *
     * @param text 时间字符串
     * @return 日期
     */
    public static LocalDate parseLocalDate(CharSequence text) {
        if (text == null) {
            return null;
        }

        return LocalDate.parse(text, DateTimeFormatter.ofPattern(NORM_DATE_PATTERN));
    }

    public static void main(String[] args) {
        System.out.println(TimeUtil.toTimestamp(LocalDateTime.now()));
        System.out.println(TimeUtil.toTimestamp(LocalDate.now()));
        System.out.println(TimeUtil.toDate(LocalDateTime.now()));
        System.out.println(TimeUtil.toDate(LocalDate.now()));
        System.out.println(TimeUtil.toString(LocalDateTime.now()));
        System.out.println(TimeUtil.toString(LocalDate.now()));
        System.out.println(TimeUtil.parseLocalDateTime("2021-04-12 11:01:02"));
        System.out.println(TimeUtil.parseLocalDate("2021-04-12"));
    }

}

输出结果

1618196882
1618156800
Mon Apr 12 11:08:02 CST 2021
Mon Apr 12 00:00:00 CST 2021
2021-04-12 11:08:02
2021-04-12
2021-04-12T11:01:02
2021-04-12