如何在GregorianCallendar中減去兩個日期？

Question

如何編寫一個函數，它返回Gregorian Callendar中兩個日期之間的天數？我應該怎樣轉換我的日期和方式？

public int substractDate(GregorianCalendar beginningDate, GregorianCalendar endingDate){ 
      return dif; 
     } 

Answer 1

使用GregorianCalendar對象是Calendar的一個子類：的

String dayPattern = "DD"; 
    SimpleDateFormat days = new SimpleDateFormat(dayPattern); 
    return Integer.parseInt(days.format(endingDate.getTimeInMillis()-beginningDate.getTimeInMillis())); 

Oracle docs