How can I compare two hours in java?

Question

I want to calculate restaurant's opened hours. I have two string, for example:

String start_hour = "09:00";
String end_hour = "18:00";

And current hour for example:

    Calendar now = Calendar.getInstance();
    String current_hour = now.get(Calendar.HOUR_OF_DAY) + ":" + now.get(Calendar.MINUTE);

I calculate open hours with this method:

    public boolean isRestaurantOpenNow() {
            try {
                Calendar now = Calendar.getInstance();
                String current_hour = now.get(Calendar.HOUR_OF_DAY) + ":" + now.get(Calendar.MINUTE);
                String st_hour = "09:00";
                String en_hour = "18:00";
                @SuppressLint("SimpleDateFormat") final SimpleDateFormat format = new SimpleDateFormat("HH:mm");
                Date sth = null;
                sth = format.parse(st_hour);
                Date enh = format.parse(en_hour);
                Date nowh = format.parse(current_hour );
                if (nowh != null) {
                    if (nowh.before(enh) && nowh.after(sth)) {
                        // restaurant is open
                        return true;
                    } else {
                        // restaurant is close
                        return false;
                    }
                }
            } catch (ParseException ignored) {
            }
            return false;
        }

But I have some problem with that. This method working wrong when start_hour is "13:00" and end_hour "05:00". Because 05:00 hour from next day. How can I solve this problem?

I recommend you don’t use `Calendar`, `SimpleDateFormat` and `Date`. Those classes are poorly designed and long outdated, `SimpleDateFormat` in particular notoriously troublesome. Instead use `LocalTime` from [java.time, the modern Java date and time API](https://docs.oracle.com/javase/tutorial/datetime/). — Ole V.V., Dec 19 '19 at 20:02

score 1 · Accepted Answer · answered Dec 19 '19 at 19:55

instead of

nowh.before(enh) && nowh.after(sth)

use

nowh.before(enh) && nowh.after(sth) && sth.before(enh)
|| enh.before(sth) && !(nowh.before(enh) && nowh.after(sth))

Apart from that I think Calendar class is supposed to be used differently I assume...

score 1 · Answer 2 · answered Dec 19 '19 at 20:21

java.time and ThreeTenABP

public boolean isRestaurantOpenNow() {
    LocalTime startHour = LocalTime.parse("13:00");
    LocalTime endHour = LocalTime.parse("05:00");

    LocalTime currentHour = LocalTime.now(ZoneId.systemDefault());
    if (startHour.isBefore(endHour)) { // Both are on the same day
        return currentHour.isAfter(startHour) && currentHour.isBefore(endHour);
    } else { // end is on the next day
        return currentHour.isBefore(endHour) || currentHour.isAfter(startHour) ;
    }
}

Trying it just now (21:20 in my time zone):

    System.out.println(isRestaurantOpenNow());

Output was:

true

Question: Doesn’t java.time require Android API level 26?

java.time works nicely on both older and newer Android devices. It just requires at least Java 6.

In Java 8 and later and on newer Android devices (from API level 26) the modern API comes built-in.
In non-Android Java 6 and 7 get the ThreeTen Backport, the backport of the modern classes (ThreeTen for JSR 310; see the links at the bottom).
On (older) Android use the Android edition of ThreeTen Backport. It’s called ThreeTenABP. And make sure you import the date and time classes from org.threeten.bp with subpackages.

Links

Oracle tutorial: Date Time explaining how to use java.time.
Java Specification Request (JSR) 310, where java.time was first described.
ThreeTen Backport project, the backport of java.time to Java 6 and 7 (ThreeTen for JSR-310).
ThreeTenABP, Android edition of ThreeTen Backport
Question: How to use ThreeTenABP in Android Project, with a very thorough explanation.

How can I compare two hours in java?

2 Answers2

java.time and ThreeTenABP

Question: Doesn’t java.time require Android API level 26?

Links

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