Java WEEK_OF_YEAR

Question

I implemented the following method:

    private int getWeek(String datum){

    SimpleDateFormat format = new SimpleDateFormat("dd.MM.yyyy");
    Date date = null;
    try {
        date = format.parse(datum);
    } catch (ParseException e) {
        e.printStackTrace();
    }
    Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone( "Europe/Berlin" ));
    calendar.setTime(date);

    int week = calendar.get(Calendar.WEEK_OF_YEAR);
    return week;
}

But when I call the method with

getWeek("01.01.2017")

it returns 52. But it should be 1. Where is my mistake?

When i call the method with

getWeek("01.01.2016")

it returns 53.

I'm pretty sure there's a better one IIRC, but https://stackoverflow.com/q/4608470/5647260 — Andrew Li, Jul 16 '17 at 14:10

score 0 · Answer 1 · answered Jul 16 '17 at 14:09

0

you have lost set the TimeZone in SimpleDateFormat, for example:

private int getWeek(String datum) {
    TimeZone zone = TimeZone.getTimeZone("Europe/Berlin");
    SimpleDateFormat format = new SimpleDateFormat("dd.MM.yyyy");

    //     v--- set the timezone here 
    format.setTimeZone(zone);

    Date date = null;
    try {
        date = format.parse(datum);
    } catch (ParseException e) {
        e.printStackTrace();
    }

    Calendar calendar = Calendar.getInstance(zone);
    calendar.setTime(date);

    int week = calendar.get(Calendar.WEEK_OF_YEAR);
    return week;
}

answered Jul 16 '17 at 14:09

holi-java

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I used your whole method to test it, it also returns 52. – sHarivaRi Jul 16 '17 at 14:22
@sHarivaRi are you sure? have you re-compiled your classes again? – holi-java Jul 16 '17 at 14:26
Yes, but your code is correct, because the 01.01.2017 is really the 52. week of year in Germany. – sHarivaRi Jul 16 '17 at 14:27
@sHarivaRi ..., I'm from China. both `01.01.2016` and `01.01.2017` output are `1` in my computer. – holi-java Jul 16 '17 at 14:29
Yeah, i guess you use another system than germany to count your week of year. – sHarivaRi Jul 16 '17 at 14:50
@sHarivaRi I think it is irrelevant. since you use the same `TimeZone`. and the output should both are `1` too in your machine. please make sure your source code / project was rebuild. – holi-java Jul 16 '17 at 14:52
Read the duplicate. It does not depend on `TimeZone`, it depends on `Locale` – Erwin Bolwidt Jul 18 '17 at 13:27

score 0 · Answer 2 · answered Jul 16 '17 at 14:25

0

Damnit.. that was a huge brain failure. 52 is the correct answer for the input.

in Germany the first Week of Year is the first week with 4 or more days in the new year.

Sorry.

answered Jul 16 '17 at 14:25

sHarivaRi

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2

It is not just Germany, it is actually an ISO standard (ISO-8601), see https://en.wikipedia.org/wiki/ISO_week_date – Mark Rotteveel Jul 16 '17 at 14:30

Java WEEK_OF_YEAR

2 Answers2