Date工具遇到的一个坑

    private Date contractBeginDate(){
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(new Date());
        calendar.add(Calendar.DATE,1);
        calendar.set(Calendar.HOUR,0);
        calendar.set(Calendar.MINUTE,0);
        calendar.set(Calendar.SECOND,0);
        calendar.set(Calendar.MILLISECOND,0);
//        calendar.set(Calendar.AM,0);
        return calendar.getTime();
    }

    private Date contractEndDate(Date beginDate){
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(beginDate);
        calendar.add(Calendar.YEAR,1);
        return calendar.getTime();
    }

calendar.set(Calendar.AM,0);
这一句会导致 代码并不是加1年 反而是减一年

测试代码:

   @Test
    public void testEndDate(){
        DateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        Date tomer = contractBeginDate();
        Date endDate = contractEndDate(tomer);
        Date yearLater = contractEndDate(new Date());

        System.out.println(format.format(new Date()));
        System.out.println(format.format(tomer));
        System.out.println(format.format(endDate));
        System.out.println(format.format(yearLater));
    }

    private Date contractEndDate(Date beginDate){
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(beginDate);
        calendar.add(Calendar.YEAR,1);
        return calendar.getTime();
    }

    private Date contractBeginDate(){
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(new Date());
        calendar.add(Calendar.DATE,1);
        calendar.set(Calendar.HOUR,0);
        calendar.set(Calendar.MINUTE,0);
        calendar.set(Calendar.SECOND,0);
        calendar.set(Calendar.MILLISECOND,0);
        calendar.set(Calendar.AM,0);
        return calendar.getTime();
    }

输出的结果:

2019-10-15 09:47:49
2019-10-16 00:00:00
2018-10-16 00:00:00
2020-10-15 09:47:49

并不是预期的

需要注意

删除这一行 就正常预期的

calendar.set(Calendar.AM,0);