参考链接1：

参考链接2：

参考链接3：

import java.time.DayOfWeek;import java.time.Duration;import java.time.LocalDate;import java.time.LocalDateTime;import java.time.LocalTime;import java.time.Period;import java.time.format.DateTimeFormatter;import java.time.temporal.Temporal;import java.time.temporal.TemporalAdjuster;import java.time.temporal.TemporalAdjusters;public class DateTimeUtils {    public static final DateTimeFormatter DATETIME_FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");    public static final DateTimeFormatter MONTH_FORMATTER    = DateTimeFormatter.ofPattern("yyyy-MM");    public static final DateTimeFormatter DATE_FORMATTER     = DateTimeFormatter.ofPattern("yyyy-MM-dd");    public static final DateTimeFormatter TIME_FORMATTER     = DateTimeFormatter.ofPattern("HH:mm:ss");    public static LocalDate parseLocalDate(String dateStr) {        return LocalDate.parse(dateStr, DATE_FORMATTER);    }    public static LocalDateTime parseLocalDateTime(String dateTimeStr) {        return LocalDateTime.parse(dateTimeStr, DATETIME_FORMATTER);    }    public static LocalTime parseLocalTime(String timeStr) {        return LocalTime.parse(timeStr, TIME_FORMATTER);    }    public static String formatLocalDate(LocalDate date) {        return date.format(DATE_FORMATTER);    }    public static String formatLocalDateTime(LocalDateTime datetime) {        return datetime.format(DATETIME_FORMATTER);    }    public static String formatLocalTime(LocalTime time) {        return time.format(TIME_FORMATTER);    }    /**     * 日期相隔天数     * @param startDateInclusive     * @param endDateExclusive     * @return     */    public static int periodDays(LocalDate startDateInclusive, LocalDate endDateExclusive) {        return Period.between(startDateInclusive, endDateExclusive).getDays();    }    /**     * 日期相隔小时     * @param startInclusive     * @param endExclusive     * @return     */    public static long durationHours(Temporal startInclusive, Temporal endExclusive) {        return Duration.between(startInclusive, endExclusive).toHours();    }    /**     * 日期相隔分钟     * @param startInclusive     * @param endExclusive     * @return     */    public static long durationMinutes(Temporal startInclusive, Temporal endExclusive) {        return Duration.between(startInclusive, endExclusive).toMinutes();    }    /**     * 日期相隔毫秒数     * @param startInclusive     * @param endExclusive     * @return     */    public static long durationMillis(Temporal startInclusive, Temporal endExclusive) {        return Duration.between(startInclusive, endExclusive).toMillis();    }    /**     * 返回当前的日期     * @return     */    public static LocalDate getCurrentLocalDate() {        return LocalDate.now();    }    /**     * 返回当前时间     * @return     */    public static LocalTime getCurrentLocalTime() {        return LocalTime.now();    }    public static LocalDateTime get() {        return LocalDateTime.now();    }    public static int getYear() {        return get().getYear();    }    public static LocalDateTime withYear(int year) {        return get().withYear(year);    }    public static int getMonth() {        return get().getMonthValue();    }    public static LocalDateTime firstDayOfThisYear(int year) {        return withYear(year).with(TemporalAdjusters.firstDayOfYear()).with(LocalTime.MIN);    }    /**     * @Title: getFirstDayOfThisYear     * @Description: 获取设置所属年最初时间     * @param year     * @return String     */    public static String getFirstDayOfThisYear(int year) {        LocalDateTime firstDayOfThisYear = firstDayOfThisYear(year);        return DATETIME_FORMATTER.format(firstDayOfThisYear);    }    public static LocalDateTime lastDayOfThisYear(int year) {        return withYear(year).with(TemporalAdjusters.lastDayOfYear()).with(LocalTime.MAX);    }    /**     * @Title: getLastDayOfThisYear     * @Description: 获取设置所属年最后时间     * @param year     * @return String     */    public static String getLastDayOfThisYear(int year) {        LocalDateTime lastDayOfThisYear = lastDayOfThisYear(year);        return DATETIME_FORMATTER.format(lastDayOfThisYear);    }    /**     * @Title: getFirstDayOfThisMonth     * @Description: 获取本月的第一天     * @return String     */    public static String getFirstDayOfThisMonth() {        LocalDateTime firstDayOfThisYear = get().with(TemporalAdjusters.firstDayOfMonth());        return DATETIME_FORMATTER.format(firstDayOfThisYear);    }    /**     * @Title: getFirstDayOfThisMonth     * @Description: 获取本月的最末天     * @return String     */    public static String getLastDayOfThisMonth() {        LocalDateTime firstDayOfThisYear = get().with(TemporalAdjusters.lastDayOfMonth());        return DATETIME_FORMATTER.format(firstDayOfThisYear);    }    /**     * @Title: plusDays     * @Description: 当前日期向后推多少天     * @param day     * @return LocalDateTime     */    public static LocalDateTime plusDays(int days) {        return get().plusDays(days);    }    /**     * @Title: firstDayOfWeekInYearMonth     * @Description: 获取指定年月的第一个周一     * @param year     * @param month     * @return LocalDateTime     */    public static LocalDateTime firstDayOfWeekInYearMonth(int year, int month) {        return get().withYear(year).withMonth(month).with(TemporalAdjusters.firstInMonth(DayOfWeek.MONDAY));    }    /**     * @Title: todayStart     * @Description: 当天开始时间     * @return LocalDateTime     */    public static LocalDateTime todayStart() {        return LocalDateTime.of(getCurrentLocalDate(), LocalTime.MIN);    }    /**     * @Title: todayEnd     * @Description: 当天结束时间     * @return LocalDateTime     */    public static LocalDateTime todayEnd() {        return LocalDateTime.of(getCurrentLocalDate(), LocalTime.MAX);    }    /**     * @Title: getStartDayOfWeekToString     * @Description: 获取周第一天     * @return String     */    public static String getStartDayOfWeekToString() {        return formatLocalDate(getStartDayOfWeek());    }    public static LocalDate getStartDayOfWeek() {        TemporalAdjuster FIRST_OF_WEEK = TemporalAdjusters.ofDateAdjuster(localDate -> localDate.minusDays(localDate                .getDayOfWeek().getValue() - DayOfWeek.MONDAY.getValue()));        return getCurrentLocalDate().with(FIRST_OF_WEEK);    }    /**     * @Title: getEndDayOfWeekToString     * @Description: 获取周最后一天     * @return String     */    public static String getEndDayOfWeekToString() {        return formatLocalDate(getEndDayOfWeek());    }    public static LocalDate getEndDayOfWeek() {        TemporalAdjuster LAST_OF_WEEK = TemporalAdjusters.ofDateAdjuster(localDate -> localDate.plusDays(                DayOfWeek.SUNDAY.getValue() - localDate.getDayOfWeek().getValue()));        return getCurrentLocalDate().with(LAST_OF_WEEK);    }    public static void main(String[] args) {        //        Integer year = 2019;        System.out.println(getFirstDayOfThisYear(year));        System.out.println(getLastDayOfThisYear(year));        //        System.out.println(DATETIME_FORMATTER.format(plusDays(1)));        System.out.println(DATETIME_FORMATTER.format(plusDays(-1)));        // 取第一个周一        LocalDate ld = LocalDate.parse("2019-01-01").with(TemporalAdjusters.firstInMonth(DayOfWeek.MONDAY));        System.out.println(DATE_FORMATTER.format(ld));        //        System.out.println(DATETIME_FORMATTER.format(firstDayOfWeekInYearMonth(year, 3)));        System.out.println("-------------------");        // new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format();        System.out.println(getStartDayOfWeekToString());        System.out.println(getEndDayOfWeekToString());        System.out.println("-------------------");        System.out.println(DATETIME_FORMATTER.format(todayStart()));        System.out.println(DATETIME_FORMATTER.format(todayEnd()));    }}