java中怎样计算两个时间如：“21:57”和“08:20”相差的分钟数、小时数

方法一：
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Date now = null;
Date date = null;
try {
now = df.parse("2004-03-26 13:31:40");
date = df.parse("2004-01-02 11:30:24");
} catch (ParseException e) {
e.printStackTrace();
}

long l = now.getTime() - date.getTime();
long day = l / (24 * 60 * 60 * 1000);
long hour = (l / (60 * 60 * 1000) - day * 24);
long min = ((l / (60 * 1000)) - day * 24 * 60 - hour * 60);
long s = (l / 1000 - day * 24 * 60 * 60 - hour * 60 * 60 - min * 60);
System.out.println("" + day + "天" + hour + "小时" + min + "分" + s + "秒");

方法二：
SimpleDateFormat dfs = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Date begin = null;
Date end = null;
try {
begin = dfs.parse("2004-01-02 11:30:24");
end = dfs.parse("2004-03-26 13:31:40");
} catch (ParseException e) {
e.printStackTrace();
}

long between = (end.getTime() - begin.getTime()) / 1000;// 除以1000是为了转换成秒

long day1 = between / (24 * 3600);
long hour1 = between % (24 * 3600) / 3600;
long minute1 = between % 3600 / 60;
long second1 = between % 60;
System.out.println("" + day1 + "天" + hour1 + "小时" + minute1 + "分"
+ second1 + "秒");

原文转自：http://topic.csdn.net/u/20110617/17/c570f97f-1f60-4290-b489-27349cfc6215.html