Question

我想要发生什么 - 如果日期（从参数给出）等于该月的最后一天，我希望成本增加10％。即如果dayOfTravel =该月的最后一天

  public static double ReturnJourneyCost(int journeyID, int dayOfTravel, int monthOfTravel, int yearOfTravel){

    Cost = Double.parseDouble(XMLLoad.load(journeyID, 3));
    return Cost;

}

Answer 1

使用旧的JDK-stuff，答案可能如下：

public static boolean isLastDayOfMonth(int year, int month, int day) {
  GregorianCalendar gcal = new GregorianCalendar(year, month - 1, day);
  gcal.add(Calendar.DATE, 1);
  return (gcal.get(Calendar.DAY_OF_MONTH) == 1);
}

在Java 8中（更好的是因为它避免了对系统时区的任何隐式引用）：

public static boolean isLastDayOfMonth(int year, int month, int day) {
  LocalDate date = LocalDate.of(year, month, day);
  return date.lengthOfMonth() == day;
}

Answer 2

使用GregorianCalendar.getActualMaximum()之类的东西可以解决这个问题：

GregorianCalendar calendar = new GregorianCalendar();
calendar.set(Calendar.YEAR, yearOfTravel);
calendar.set(Calendar.MONTH, monthOfTravel); // warning: 0-based!
calendar.set(Calendar.DAY_OF_MONTH, dayOfTravel);

int daysInThisMonth = calendar.getActualMaximum(Calendar.DAY_OF_MONTH);
if (daysInThisMonth == dayOfTravel)
{
    // increase cost by 10%
}

Answer 3

你需要写一些自定义代码......

public boolean isLastDay(Date date) {
    Calendar now = Calendar.getInstance();
    now.setTime(date);
    Calendar c = Calendar.getInstance();
    c.setTime(date);

    c.add(Calendar.DAY_OF_MONTH, 1);
    return c.get(Calendar.MONTH) != now.get(Calendar.MONTH);
}

Answer 4

你可以试试这个：

Calendar calendar = Calendar.getInstance();

if (calendar.get(Calendar.MONTH) == monthOfTravel && 
&& calendar.ger(Calendar.YEAR) == yearOfTravel && calendar.getActualMaximum(Calendar.DAY_OF_MONTH) == dayOfTravel) {
//...
}

这是一个月的最后一天吗？

4 个答案: