From Java Date Object find if it's first day of the month

Question

From java.util.Date, What is the easiest/smart way to find out if it's the first day of a month ?

Answer 1

With the "classic" Java API (pre Java 8):

public static boolean isFirstDayOfMonth(final Date date)
{
    final Calendar cal = Calendar.getInstance();
    cal.setTime(date);
    final int dom = cal.get(Calendar.DAY_OF_MONTH);
    return dom == 1;
}

Then you just call it like this:

isFirstDayOfMonth(new Date());

Answer 2

Calendarclass is better for such things.

But if you really want to do this with Date only, then

        Date d = new Date();
        d = new Date(d.getYear(), d.getMonth(), 0);

        switch (d.getDay()) {
        case 0: System.out.println("Monday");
        break;
        case 1: System.out.println("Tuesday");
        break;
        case 2: System.out.println("Wednessday");
        break;
        case 3: System.out.println("Thusrday");
        break;
        case 4: System.out.println("Friday");
        break;
        case 5: System.out.println("Satureday");
        break;
        case 6: System.out.println("Sunday");
        break;
        }

Answer 3

Java 8

Date date = new Date();
Instant instant = date.toInstant();
int dom = LocalDateTime.
        ofInstant(instant, ZoneId.systemDefault()).
        getDayOfMonth();
System.out.println(dom);

Joda Time (Pre Java 8)

Date date = new Date();
int dom = LocalDateTime.fromDateFields(date).getDayOfMonth();
System.out.println(dom);