按指定的天數計算日期

Question

我使用Android Studio。我想從我指定的日期算起280天后的那一天。

Calendar thatDay = Calendar.getInstance(); //today date 
thatDay.set(Calendar.DAY_OF_MONTH,selectedday); 
thatDay.set(Calendar.MONTH,selectedmonth-1); // 0-11 so 1 less 
thatDay.set(Calendar.YEAR, selectedyear); 


Calendar afterday= Calendar.getInstance(); //280 after date 
afterday.set(Calendar.DAY_OF_MONTH,selectedday+10); 
afterday.set(Calendar.MONTH,selectedmonth+8); 
afterday.set(Calendar.YEAR, selectedyear); 

Log.e(" After Day: ", " days:" + (afterday.getTimeInMillis()- thatDay.getTimeInMillis())/ (24 * 60 * 60 * 1000)); 

日誌輸出變量。有時285283279種

Answer 1

只需cal.add(Calendar.DATE, 280);

Answer 2

LocalDate myDate = LocalDate.now(); 
    LocalDate datePlusDays = myDate.plusDays(280); 
    System.out.println("Today Plus 280 Days: " + datePlusDays);