获取当前时间的周一

package com.alpari.wang.utils;

import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Component;

import java.util.Calendar;
import java.util.Date;

@Slf4j
@Component
public class DateUtils {

    private DateUtils() {

    }

    /**
     * 根据year年所在第week周，获取周一的时间，以及所在月份 获取Calendar
     * @param year 年份
     * @param week 当前年所在的第几周，以每年的第一个周一为第一周
     * @return 获取Calendar 可获取周一的时间，以及所在月份
     */
    public static Calendar weekToDayFormate(Integer year, Integer week){

        Calendar cal = Calendar.getInstance();
        cal.set(Calendar.YEAR, year);
        cal.set(Calendar.WEEK_OF_YEAR, week);
        cal.setFirstDayOfWeek(Calendar.MONDAY);
        cal.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
        //一年第一周最小天数为4天，按照iso标准计算
        cal.setMinimalDaysInFirstWeek(4);
        cal.set(Calendar.HOUR_OF_DAY, 0);
        cal.set(Calendar.MINUTE, 0);
        cal.set(Calendar.SECOND, 0);
        cal.set(Calendar.MILLISECOND, 0);
        return cal;
    }

    /**
     * 根据任意日期获取当前周周一时间（第一种）
     * @param date
     * @return
     */
    public static Date getMonday(Date date) {
        Calendar c = Calendar.getInstance();
        c.setTime(date);
        c.setFirstDayOfWeek(Calendar.MONDAY);
        c.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
        return org.apache.commons.lang3.time.DateUtils.truncate(c.getTime(), Calendar.DATE);
    }

    /**
     * 根据任意日期获取当前周周一时间（第二种）
     * @param date
     * @return
     */
    public static Date getWeekBegin1(Date date) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        calendar.setFirstDayOfWeek(Calendar.MONDAY);
        calendar.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
        return DateUtils.getDayStartTime(calendar.getTime());
    }

    /**
     * 根据任意日期获取当前周周一时间（第三种）
     * @param date
     * @return
     */
    public static Date getWeekBegin2(Date date) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        int week = calendar.get(Calendar.WEEK_OF_YEAR);
        int weekDay = calendar.get(Calendar.DAY_OF_WEEK);
        if (weekDay == 1) {
            week = week - 1;
        }
        calendar.setWeekDate(calendar.getWeekYear(), week, Calendar.MONDAY);
        calendar.set(calendar.get(Calendar.YEAR),
                calendar.get(Calendar.MONTH),
                calendar.get(Calendar.DAY_OF_MONTH),
                0, 0, 0);
        return DateUtils.getDayStartTime(calendar.getTime());
    }

    /**
     * 获取入参时间所在年周xxxx年xx周6位
     * @param date
     * @return
     */
    public static String getYearWeek(Date date) {
        Calendar cal = Calendar.getInstance();
        //设置一周起始时间为周一
        cal.setFirstDayOfWeek(Calendar.MONDAY);
        //一年第一周最小天数为4天，按照iso标准计算
        cal.setMinimalDaysInFirstWeek(4);
        cal.setTime(date);
        //设置装运日期所在的年周
        String yearWeek;
        //跨年,当前时间为一月初，按照iso算法为去年的第52或者53周，故年分减一
        if(cal.get(Calendar.MONTH) + 1 == 1 && 52 <= cal.get(Calendar.WEEK_OF_YEAR)) {
            yearWeek = cal.get(Calendar.YEAR) - 1 + String.format("%02d", cal.get(Calendar.WEEK_OF_YEAR));
        }
        //当前时间为12月，按照iso算法周数为下一年第一周，故年份加一
        else if(cal.get(Calendar.MONTH) + 1 == 12 && 1 == cal.get(Calendar.WEEK_OF_YEAR)) {
            yearWeek = cal.get(Calendar.YEAR) + 1 + String.format("%02d", cal.get(Calendar.WEEK_OF_YEAR));
        }
        else {
            yearWeek = cal.get(Calendar.YEAR) + String.format("%02d", cal.get(Calendar.WEEK_OF_YEAR));
        }
        return yearWeek;
    }
}