How to check if the current date is the first of the month

Question

I'm trying to write a function which involves checking if the current date is the first of the month such as 01/03/2015 for example and then run something depending if it is.

It doesn't matter whether it is a date or calendar object, I just want to check if the current date when the code is run is the first of the month

@taimeili123 yes that's what I mean sorry it was badly worded — Nick Karaolis, Mar 30 '15 at 13:38
@NickKaraolis is the date format always gonna be `MM/DD/YYYY`? — OPK, Mar 30 '15 at 13:40
possible duplicate of [How can Joda or Java returns true if day is the first day of the month?](http://stackoverflow.com/questions/24451419/how-can-joda-or-java-returns-true-if-day-is-the-first-day-of-the-month) — Basil Bourque, Mar 31 '15 at 07:09

But I'm Not A Wrapper Class · Accepted Answer · 2018-05-18T13:06:26.537

12

There's a getter for that:

public boolean isFirstDayofMonth(Calendar calendar){
    if (calendar == null) {
        throw new IllegalArgumentException("Calendar cannot be null.");
    }

    int dayOfMonth = calendar.get(Calendar.DAY_OF_MONTH);
    return dayOfMonth == 1;
}

edited May 18 '18 at 13:06

answered Mar 30 '15 at 13:41

But I'm Not A Wrapper Class

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An exception or an `Optional` is ways better than returning `false`on `null` – Oleg Sklyar May 18 '18 at 06:50
@OlegSkylar That is context dependent, but I agree. I will update. – But I'm Not A Wrapper Class May 18 '18 at 13:03

Michal Maťovčík · Answer 2 · 2018-05-18T06:47:38.050

6

Java 8 solution with LocalDate and TemporalAdjuster

first day of month:

someDate.isEqual(someDate.with(firstDayOfMonth()))

last day of month:

someDate.isEqual(someDate.with(lastDayOfMonth())

This solution uses TemporalAdjusters utility from java.time.temporal. It is common practice to use it as import static but you can also use it as TemporalAdjusters.lastDayOfMonth()

edited May 18 '18 at 06:47

answered May 17 '18 at 08:38

Michal Maťovčík

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3

Nice that someone at last (after three years) provided the `java.time` answer, the modern answer. Thanks. Still simpler: `someDate.getDayOfMonth() == 1`. – Ole V.V. May 17 '18 at 12:46
1

You should explain where `first/lastDayOfMonth()` comes from. – Basil Bourque May 18 '18 at 01:53

score 2 · Answer 3 · edited Mar 20 '23 at 13:01

2

public static boolean isFirstDayOfTheMonth(Date dateToday){
    Calendar cal = Calendar.getInstance();
    c.setTime(dateToday );

    if (c.get(Calendar.DAY_OF_MONTH) == 1) {
      return true;
    }
    return false;
}

edited Mar 20 '23 at 13:01

Loïc Gammaitoni

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answered Feb 09 '16 at 09:49

Kranthi Kumar Kota

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2

Generally better to use Calendar.getInstance() and let the JVM decide which Calendar to use rather than enforcing the use of GregorianCalendar – Loïc Gammaitoni Mar 20 '23 at 13:03

How to check if the current date is the first of the month

3 Answers3