Java Data Type - 如何计算两个日期之间的天数

import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;

public class Main {
  public static void main(String args[]) {
    Calendar cal1 = new GregorianCalendar();
    Calendar cal2 = new GregorianCalendar();

    cal1.set(2010, 12, 1);
    cal2.set(2011, 9, 31);
    System.out.println("Days= " + daysBetween(cal1.getTime(), cal2.getTime()));
  }

  public static int daysBetween(Date d1, Date d2) {
    return (int) ((d2.getTime() - d1.getTime()) / (1000 * 60 * 60 * 24));
  }
}