Java 計算時間間隔

public static void main(String[] args) throws ParseException {
long d1,d2,d3;
ArrayList<String> list = new ArrayList();
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
Calendar calendar = new GregorianCalendar();
String datestr1 = "2010-01-01";
String datestr2 = "2011-03-01";
d1 = df.parse(datestr2).getTime();
d2 = df.parse(datestr1).getTime();
d3 = Math.abs((d1-d2)/1000/60/60/24);//時間間隔
for (int i = 0; i <= d3; i++) {
calendar.setTime(java.sql.Date.valueOf(datestr1));
calendar.add(calendar.DATE,i);//得到下一天時間
list.add(df.format(calendar.getTime()).toString());
}
for (int i = 0; i < list.size(); i++) {
System.out.println(list.get(i));
}
}