Java Data Type - 如何计算两个日期之间的天数

import java.util.Calendar;

public class Main {
  public static void main(String[] args) {
    Calendar startEmployment = Calendar.getInstance();
    startEmployment.set(2010, 2, 1);
    startEmployment.set(2011, Calendar.FEBRUARY, 1);

    Calendar now = Calendar.getInstance();

    long numberOfDays1 = countDays(startEmployment, now);

    System.out.println(numberOfDays1);
  }

  private static long countDays(Calendar start, Calendar end) {
    long totalNumberOfDays = 0;
    while (start.before(end)) {
      start.add(Calendar.DAY_OF_MONTH, 1);
      totalNumberOfDays++;
    }
    return totalNumberOfDays;
  }
}