For Example I have the date: \"23/2/2010\" (23th Feb 2010). I want to pass it to a function which would return the day of week. How can I do this?
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Yes. Depending on your exact case:
You can use java.util.Calendar:
Calendar c = Calendar.getInstance();
c.setTime(yourDate);
int dayOfWeek = c.get(Calendar.DAY_OF_WEEK);
if you need the output to be Tue rather than 3 (Days of week are indexed starting at 1 for Sunday, see Calendar.SUNDAY), instead of going through a calendar, just reformat the string: new SimpleDateFormat("EE").format(date) (EE meaning "day of week, short version")
if you have your input as string, rather than Date, you should use SimpleDateFormat to parse it: new SimpleDateFormat("dd/M/yyyy").parse(dateString)
you can use joda-time's DateTime and call dateTime.dayOfWeek() and/or DateTimeFormat.
edit: since Java 8 you can now use java.time package instead of joda-time