Android指定日期加任意天数后返回相加后的日期

第一个想到的是开源库，无奈，好用但是太大了600多kb o(╥﹏╥)o
implementation 'net.danlew:android.joda:2.9.5'

public static String plusDay(int num, String newDate) {
  DateTimeFormatter formatter = DateTimeFormat.forPattern("yyyy-MM-dd");
  return DateTime.parse(newDate, formatter).plusDays(num).toString("yyyy-MM-dd");  
}

开始找android的Calendar 类处理这个问题。

public static String plusDay(int num, String newDate) {
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd", Locale.CHINA);
    Date date = null;
    try {
        date = sdf.parse(newDate);
        Calendar rightNow = Calendar.getInstance();
        rightNow.setTime(date);
        rightNow.add(Calendar.DAY_OF_YEAR, +num);
        Date time = rightNow.getTime();
        String format = sdf.format(time);
        return format;
    } catch (ParseException e) {
        e.printStackTrace();
    }
    return newDate;
}