在java中得到日期之间的天数差异

Question

我正在尝试这样的事情，我试图从组合框中获取日期

Calendar start = Calendar.getInstance();
Calendar end = Calendar.getInstance();

int Sdate=Integer.parseInt(cmbSdate.getSelectedItem().toString());  
int Smonth=cmbSmonth.getSelectedIndex();
int Syear=Integer.parseInt(cmbSyear.getSelectedItem().toString());

int Edate=Integer.parseInt(cmbEdate.getSelectedItem().toString());
int Emonth=cmbEmonth.getSelectedIndex();
int Eyear=Integer.parseInt(cmbEyear.getSelectedItem().toString());

start.set(Syear,Smonth,Sdate);  
end.set(Eyear,Emonth,Edate);

DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
String startdate=dateFormat.format(start.getTime());  
String enddate=dateFormat.format(end.getTime());

我无法减去结束日期和开始日期如何获得开始日期和结束日期之间的差额？

Answer 1

Calendar start = Calendar.getInstance();
    Calendar end = Calendar.getInstance();
    start.set(2010, 7, 23);
    end.set(2010, 8, 26);
    Date startDate = start.getTime();
    Date endDate = end.getTime();
    long startTime = startDate.getTime();
    long endTime = endDate.getTime();
    long diffTime = endTime - startTime;
    long diffDays = diffTime / (1000 * 60 * 60 * 24);
    DateFormat dateFormat = DateFormat.getDateInstance();
    System.out.println("The difference between "+
      dateFormat.format(startDate)+" and "+
      dateFormat.format(endDate)+" is "+
      diffDays+" days.");

如orange80所指出的，在超过夏令时（或leap秒）时，这将不起作用，并且在一天中的不同时间使用时，也可能无法给出预期的结果。使用JodaTime可能更容易获得正确的结果，因为我知道8之前纯Java的唯一正确方法是使用Calendar的add和before/ after方法检查和调整计算：

    start.add(Calendar.DAY_OF_MONTH, (int)diffDays);
    while (start.before(end)) {
        start.add(Calendar.DAY_OF_MONTH, 1);
        diffDays++;
    }
    while (start.after(end)) {
        start.add(Calendar.DAY_OF_MONTH, -1);
        diffDays--;
    }