Automatically calculate age after focus change [closed]

Answer 1

A FocusListener will help, for example...

    JXDatePicker dp = new JXDatePicker();
    dp.getEditor().addFocusListener(new FocusAdapter() {
        @Override
        public void focusLost(FocusEvent e) {
            // Calculate age
            Date date = dp.getDate();
        }
    });

See How to Write a Focus Listener for more details

The age calculation is best done using either JodaTime or Java 8's new Time API

Java 8

Date date = // Date from date picker
LocalDate ld = date.toInstant().atZone(ZoneId.systemDefault()).toLocalDate();

//LocalDate ld = LocalDate.of(1972, Month.MARCH, 8);
Period p = Period.between(ld, LocalDate.now());
System.out.println(p.getYears());
System.out.println(p.getMonths());
System.out.println(p.getDays());

Which outputs something like...

42
11
18

Joda-Time

Date date = // Date from date picker
LocalDate ld = LocalDate.fromDateFields(date);

Period p = Period.fieldDifference(ld, LocalDate.now());
System.out.println(p.getYears());
System.out.println(p.getMonths());
System.out.println(p.getDays());