【java计算日期属于本月第几周通用方法】

import java.time.DayOfWeek;
import java.time.LocalDate;
import java.time.temporal.TemporalAdjusters;public class CurrentWeekOfMonth {public static void main(String[] args) {LocalDate today = LocalDate.now();// 测试用例（可以取消注释测试特定日期）// LocalDate today = LocalDate.of(2023, 12, 3); // 测试跨年情况// LocalDate today = LocalDate.of(2023, 11, 30); // 测试月末情况WeekInfo weekInfo = getWeekNumberOfMonth(today);System.out.println("当前日期: " + today);if (weekInfo.isLastWeekOfPreviousMonth()) {System.out.println("属于上月第 " + weekInfo.getWeekNumber() + " 周");} else {System.out.println("是本月第 " + weekInfo.getWeekNumber() + " 周");}}public static WeekInfo getWeekNumberOfMonth(LocalDate date) {LocalDate firstDayOfMonth = date.with(TemporalAdjusters.firstDayOfMonth());DayOfWeek firstDayOfWeek = firstDayOfMonth.getDayOfWeek();// 确定本月第一周的开始日期LocalDate startOfFirstWeek;if (firstDayOfWeek == DayOfWeek.MONDAY) {startOfFirstWeek = firstDayOfMonth;} else {startOfFirstWeek = firstDayOfMonth.with(TemporalAdjusters.next(DayOfWeek.MONDAY));}// 如果日期在本月第一周开始之前，则属于上月的最后一周if (date.isBefore(startOfFirstWeek)) {LocalDate lastDayOfPreviousMonth = firstDayOfMonth.minusDays(1);int lastMonthWeekCount = getMonthWeekCount(lastDayOfPreviousMonth);return new WeekInfo(lastMonthWeekCount, true);}// 计算当前日期与第一周开始日期的周数差long weeksBetween = java.time.temporal.ChronoUnit.WEEKS.between(startOfFirstWeek, date);return new WeekInfo((int) weeksBetween + 1, false);}// 计算指定日期所在月份的总周数private static int getMonthWeekCount(LocalDate dateInMonth) {LocalDate firstDay = dateInMonth.with(TemporalAdjusters.firstDayOfMonth());LocalDate lastDay = dateInMonth.with(TemporalAdjusters.lastDayOfMonth());DayOfWeek firstDayOfWeek = firstDay.getDayOfWeek();LocalDate startOfFirstWeek;if (firstDayOfWeek == DayOfWeek.MONDAY) {startOfFirstWeek = firstDay;} else {startOfFirstWeek = firstDay.with(TemporalAdjusters.next(DayOfWeek.MONDAY));}// 如果第一周开始日期在第一天之后，则第一周可能很短long weeks = java.time.temporal.ChronoUnit.WEEKS.between(startOfFirstWeek, lastDay) + 1;// 处理月末最后几天是否构成完整一周LocalDate endOfLastWeek = startOfFirstWeek.plusWeeks(weeks - 1).with(TemporalAdjusters.nextOrSame(DayOfWeek.SUNDAY));if (lastDay.isAfter(endOfLastWeek)) {weeks++;}return (int) weeks;}// 用于返回周数和是否属于上月的辅助类static class WeekInfo {private final int weekNumber;private final boolean lastWeekOfPreviousMonth;public WeekInfo(int weekNumber, boolean lastWeekOfPreviousMonth) {this.weekNumber = weekNumber;this.lastWeekOfPreviousMonth = lastWeekOfPreviousMonth;}public int getWeekNumber() {return weekNumber;}public boolean isLastWeekOfPreviousMonth() {return lastWeekOfPreviousMonth;}}
}