public static List<Map<String, String>> getWeekDayInMonth(String date)
{
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
    List<Map<String, String>> resultList = new ArrayList<>();
    String[] weeks = { "星期日", "星期一", "星期二", "星期三", "星期四", "星期五", "星期六" };
    Calendar calendar = Calendar.getInstance();
    try
    {
        calendar.setTime(sdf.parse(date));
    }
    catch (Exception e)
    {
        e.printStackTrace();
    }
    int days = calendar.getActualMaximum(Calendar.DAY_OF_MONTH);
    int weekday = calendar.get(Calendar.DAY_OF_WEEK) - 1;// 1是星期日
    String cWeekDay = weeks[weekday];
    Map<String, String> fristDate = new HashMap<>();
    fristDate.put("code", weekday + "");
    fristDate.put("weekday", cWeekDay);
    fristDate.put("date", sdf.format(calendar.getTime()));
    resultList.add(fristDate);
    for (int i = 1; i < days; i++)
    {
        calendar.add(calendar.DATE, 1);
        int weekday2 = calendar.get(Calendar.DAY_OF_WEEK) - 1;// 1是星期日
        String cWeekDay2 = weeks[weekday2];
        Map<String, String> map = new HashMap<>();
        map.put("code", weekday2 + "");
        map.put("weekday", cWeekDay2);
        map.put("date", sdf.format(calendar.getTime()));
        resultList.add(map);
    }
    return resultList;
}

public static void main(String[] args){

    try {
        List<Map<String, String>> list=getWeekDayInMonth("2022-03-01");
        for(Map<String, String> li:list){
            System.out.println(li);
        }
    } catch (Exception e) {
        e.printStackTrace();
    }

}