如何比较 Java 8 中 Date 对象之间的时间？

Question

Given two Date objects that include hours and minutes, how can I elegantly find out which one of them has the earliest time of the day?

Eg if date1 is 2018-01-01 at 09:00 , and date2 is 2018-01-02 at 08:00 , then per this specification, date2 < date1 .

Answer 1

You can use the compareTo -Method of LocalTime if you convert the Date before.

Convert like this (found at https://www.baeldung.com/java-date-to-localdate-and-localdatetime ):

public static LocalTime convertToLocalTimeViaInstant(Date dateToConvert) {
    return dateToConvert.toInstant()
            .atZone(ZoneId.systemDefault())
            .toLocalTime();
}

and compare like this:

time1.compareTo(time2);

---

If u want to use a method u can use the conversion like this:

public static int compareTimeOfDates(Date date1, Date date2) {
    return convertToLocalTimeViaInstant(date1).compareTo(convertToLocalTimeViaInstant(date2));
}

Answer 2

You can try to do something like:

boolean compareTime(Date date1, Date date2) {
    DateFormat df = new SimpleDateFormat("HHmm");
    int timeDate1 = Integer.valueOf(df.format(date1));
    int timeDate2 = Integer.valueOf(df.format(date2));
    return timeDate1 >= timeDate2;
}

Answer 3

Edit 2:

//just a sample. base on your case, set the date you have to here.
        Date date1 = Calendar.getInstance().getTime(); 
        Date date2 = Calendar.getInstance().getTime();

        LocalDateTime lcdate1 = date1.toInstant().atZone(ZoneId.systemDefault()).toLocalDateTime();
        LocalDateTime lcdate2 = date2.toInstant().atZone(ZoneId.systemDefault()).toLocalDateTime();


        int date1Hour = lcdate1.getHour();
        int date1Minute = lcdate1.getMinute();

        int date2Hour = lcdate2.getHour();
        int date2Minute = lcdate2.getMinute();

More detail is here: https://docs.oracle.com/javase/8/docs/api/java/time/LocalDateTime.html

Hope this help.

Answer 4

int compareTimeOfDate(Date a, Date b) {
    LocalDateTime localA = a.toInstant().atZone(ZoneId.systemDefault()).toLocalDateTime();
    int hourA = localA.getHour();
    int minuteA = localA.getMinute();

    LocalDateTime localB = date1.toInstant().atZone(ZoneId.systemDefault()).toLocalDateTime();
    int hourB = localB.getHour();
    int minuteB = localB.getMinute();

    if (hourA == hourB && minuteA == minuteB) {
        return 0;
    }

    if (hour1 < hour2 || hour1 == hour2 && minute1 < minute2) {
        return -1;
    }

    return 1;
}