java - 比较时间戳时，年份转到 1970

Question

我需要比较当前时间是否在 X+30 和 X-30 之间。

时间戳一切正常，但比较年份设置为 1970 年；所以输出不准确。

String string1 = "04:41 PM";
        Calendar calendar1,calendar2,calendar3,calendar4 ;
        DateFormat time1;
        Date time;
        try {
            time1 =new SimpleDateFormat("hh:mm a");
            time = time1.parse(string1);
            calendar1 = Calendar.getInstance();
            calendar1.setTime(time);
            System.out.println(time1.format(calendar1.getTime()));
            calendar2 = Calendar.getInstance();
            calendar2.setTime(time);
            calendar2.add(Calendar.MINUTE,30);
            System.out.println(time1.format(calendar2.getTime()));
            calendar3 = Calendar.getInstance();
            calendar3.setTime(time);
            calendar3.add(Calendar.MINUTE,-30);
            System.out.println(time1.format(calendar3.getTime()));

            calendar4=Calendar.getInstance();

            System.out.println(time1.format(calendar4.getTime()));
            Date now = calendar4.getTime();
            if (now.after(calendar3.getTime()) && now.before(calendar2.getTime())) {
                //checkes whether the current time is between 14:49:00 and 20:11:13.
                System.out.println(true);
            }
        } catch (ParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

Answer 1

在hh:mm a格式中YEAR字段是set to 1970 by default .

Unix time, or POSIX time, is a system for describing points in time, defined as the number of seconds elapsed since midnight proleptic Coordinated Universal Time (UTC) of January 1, 1970, not counting leap seconds.

因此，在您的情况下，您希望在比较日期时忽略 YEAR、MONTH 和 DAY_OF_MONTH 字段，所以这样做(这会重置 YEAR、MONTH 和 DAY_OF_MONTH 字段):

calendar4.setTime(time1.parse(time1.format(calendar4.getTime())));

之后:

calendar4=Calendar.getInstance();