Java 获取本周、本月的日期数组

private List getFormatDate(String type) {
    Calendar calendar = Calendar.getInstance();
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

    List list = new ArrayList<>();

    if ("day".equals(type)) {
        list.add(sdf.format(calendar.getTime()));

    } else if ("month".equals(type)) {
        int index = calendar.get(Calendar.DAY_OF_MONTH);
        for (int i = 0; i < index; i++) {
            list.add(sdf.format(calendar.getTime()));
            calendar.add(Calendar.DAY_OF_MONTH, -1);
        }

    } else {
        int index = calendar.get(Calendar.DAY_OF_WEEK) == 1 ? 7 : calendar.get(Calendar.DAY_OF_WEEK) - 1;
        for (int i = 0; i < index; i++) {
            list.add(sdf.format(calendar.getTime()));
            calendar.add(Calendar.DAY_OF_MONTH, -1);
        }
    }

    // 日期翻转，本来是从大到小，翻转成从小到大
    Collections.reverse(list);
    return list;
}

// Main方法测试
public static void main(String[] args) {
    // 获取本日日期数组
    List days = getFormatDate("day");
    System.out.println(JSONObject.toJSonString(days));

    // 获取本周日期数组
    List weeks = getFormatDate("week");
    System.out.println(JSONObject.toJSonString(weeks));

    // 获取本月日期数组
    List months = getFormatDate("month");
    System.out.println(JSONObject.toJSonString(months));

    // 默认
    List defs = getFormatDate("abc");
    System.out.println(JSONObject.toJSonString(defs));
}

// 如果你想改成其他日期做测试，只需要替换方法的第一行为：
Calendar calendar = DateUtil.toCalendar(DateUtil.getDateOfStr("2022-01-01"));


// 测试结果
["2022-01-12"]
["2022-01-10","2022-01-11","2022-01-12"]
["2022-01-01","2022-01-02","2022-01-03","2022-01-04","2022-01-05","2022-01-06","2022-01-07","2022-01-08","2022-01-09","2022-01-10","2022-01-11","2022-01-12"]
["2022-01-10","2022-01-11","2022-01-12"]