java sort list by current date then by date comparison

Question

I have an ArrayList of objects Foo(int id, Date date).

How would i go about sorting this ArrayList to look something like below

    id = 3, date = 07 Nov 2016
    id = 2, date = 08 Nov 2016
    id = 5, date = 30 Nov 2016
    id = 1, date = 05 Nov 2016
    id = 4, date = 04 Nov 2016

The top three objects are in the future sorted by closest (to the present) first, bottom two are in the past sorted by closest (to the present) first.

It's not a duplicate. It's trickier than just sorting by a property. — janos, Nov 06 '16 at 07:26
And a duplicate of [*How to sort an AreayList using multiple sorting criteria*](http://stackoverflow.com/q/3704804). **Search Stack Overflow** before posting. — Basil Bourque, Nov 06 '16 at 16:40

score 1 · Answer 1 · answered Nov 06 '16 at 07:03

1

Sort list by date, find the last item with date less than today, move items from the first to the found item to the end of the list.

answered Nov 06 '16 at 07:03

kgeorgiy

1,477
7
9

Thank you for the reply, i did not quite understand what you meant. – Ali Ihsan Nov 06 '16 at 07:49

score 1 · Accepted Answer · answered Nov 06 '16 at 07:24

To sort by multiple criteria, you need a composite comparator:

Collections.sort(dates, (d1, d2) -> {
    if (d1.after(now) && d2.after(now)) {
        return d1.compareTo(d2);
    }
    if (d1.before(now) && d2.before(now)) {
        return -d1.compareTo(d2);
    }
    return -d1.compareTo(d2);
});

That is:

If both dates are after now, sort them in normal order (increasing)
If both dates are before now, sort them in reverse order (decreasing)
Otherwise (= one date is before now, the other is after), sort them in reverse order (= newer date comes first, older comes later)

Thank you its sorting properly. – Ali Ihsan Nov 06 '16 at 07:48 — Ali Ihsan, Nov 06 '16 at 07:48

java sort list by current date then by date comparison

2 Answers2