字符串转时间须要注意!!!

public class Test {

    public static void main(String[] args)throws Exception {
        //天天上班时间 8:30
        String workDateStr="2018-07-01 8:30:00";
        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
        Date workDate = dateFormat.parse(workDateStr);
        //获取当前时间
        String nowDateStr="2018-07-01 12:01:00";
        Date nowDate = dateFormat.parse(nowDateStr);

        long time = nowDate.getTime()- workDate.getTime();
        System.out.println("time="+time);
        int hour = (int) (time/1000/60/60);
        System.out.println(hour);
    }
}

输出:

time=-30540000
-8

发现不对呀!!!时间怎么是负数？？？

一万个草泥马奔腾而来!!!

后来发现

SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");

hh:表明12小时制

HH:表明24小时制