Why does new java.text.SimpleDateFormat("EEEE").format(new java.util.Date(2015, 6, 9)) return the wrong day of the week?

Question

I want to get the day of the week from a date in Java. Why would this return Friday when it is, in fact, Tuesday?

new java.text.SimpleDateFormat("EEEE").format(new java.util.Date(2015, 6, 9))

PS I know java.util.Date(int year, int month, int day) is deprecated, maybe that has something to do with it.

Answer 1

The month argument in that deprecated constructor starts at 0 for January, so you probably wanted new Date(115, 5, 9) if you're talking about June 9th (the 115 is because the year argument is "since 1900").

From the documentation:

Parameters:

year - the year minus 1900.

month - the month between 0-11.

date - the day of the month between 1-31.

(My emphasis.)

You've said you want to do this as a one-liner. In Java 8, you could do:

String day = LocalDate.of(2015, 6, 9).format(DateTimeFormatter.ofPattern("EEEE"));

that uses java.time.LocalDate and java.time.format.DateTimeFormatter.