Titan專欄

看完了jdk的help，發現sun沒有提供這樣的一個函數，朋友給了幾個實現方法

//取得剩余天數
   SimpleDateFormat df=new SimpleDateFormat("yyyymmdd");
   Date d0=new java.util.Date();
   Date d1=df.parse(end_date);
   long time0=d0.getTime();
   long time1=d1.getTime();
   System.out.println((time1-time0)/(1000*60*60*24));

這樣算兩個時間相差的天數比較好

/**
     * 計算兩個日期之間相差的天數
     *
     * @param date1
     * @param date2
     * @return
     */
    public static int diffdates(Date date1, Date date2) {
        int result = 0;
        ElapsedTime et = new ElapsedTime();

        GregorianCalendar gc1 = new GregorianCalendar();
        GregorianCalendar gc2 = new GregorianCalendar();

        gc1.setTime(date1);
        gc2.setTime(date2);
        result = et.getDays(gc1, gc2);

        return result;
    }

然后ElapseTime中的方法是：
public int getDays(GregorianCalendar g1, GregorianCalendar g2) {
  int elapsed = 0;
  GregorianCalendar gc1, gc2;

  if (g2.after(g1)) {
   gc2 = (GregorianCalendar) g2.clone();
   gc1 = (GregorianCalendar) g1.clone();
  } else {
   gc2 = (GregorianCalendar) g1.clone();
   gc1 = (GregorianCalendar) g2.clone();
  }

  gc1.clear(Calendar.MILLISECOND);
  gc1.clear(Calendar.SECOND);
  gc1.clear(Calendar.MINUTE);
  gc1.clear(Calendar.HOUR_OF_DAY);

  gc2.clear(Calendar.MILLISECOND);
  gc2.clear(Calendar.SECOND);
  gc2.clear(Calendar.MINUTE);
  gc2.clear(Calendar.HOUR_OF_DAY);

  while (gc1.before(gc2)) {
   gc1.add(Calendar.DATE, 1);
   elapsed++;
  }
  return elapsed;
 }
其實使用joda最簡單

public boolean isRentalOverdue(DateTime datetimeRented) {
  Period rentalPeriod = Period.days(2);
  return datetimeRented.plus(rentalPeriod).isBeforeNow()
}