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;          }  }