public static Long dateDiff(String startTime, String endTime,  String format, String str) {

        // 按照传入的格式生成一个simpledateformate对象

        SimpleDateFormat sd = new SimpleDateFormat(format);

        long nd = 1000 * 24 * 60 * 60;// 一天的毫秒数

        long nh = 1000 * 60 * 60;// 一小时的毫秒数

        long nm = 1000 * 60;// 一分钟的毫秒数

        long ns = 1000;// 一秒钟的毫秒数

        long diff;

        long day = 0;

        long hour = 0;

        long min = 0;

        long sec = 0;

        // 获得两个时间的毫秒时间差异

        try {

            diff = sd.parse(endTime).getTime() - sd.parse(startTime).getTime();

            day = diff / nd;// 计算差多少天

            hour = diff % nd / nh + day * 24;// 计算差多少小时

            min = diff % nd % nh / nm + day * 24 * 60;// 计算差多少分钟

            sec = diff % nd % nh % nm / ns;// 计算差多少秒

            // 输出结果

            System.out.println("时间相差：" + day + "天" + (hour - day * 24) + "小时"

                    + (min - day * 24 * 60) + "分钟" + sec + "秒。");

            System.out.println("hour=" + hour + ",min=" + min);

            if (str.equalsIgnoreCase("h")) {

                return hour;

            } else {

                return min;

            }  

        } catch (ParseException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }

        if (str.equalsIgnoreCase("h")) {

            return hour;

        } else {

            return min;

        }

}