Sort List by dates when the first date is today

Question

Currently I am trying to sort my list by dates:

Collections.sort(unsortedDates, new Comparator<Item>() {
    public int compare(Item m1, Item m2) {
        return m1.getDate().compareTo(m2.getDate());
    }
});

But I want the list to be sorted so the anchor date will be today, the first item should be the closest date for the current date.

The date format is MM/dd.

getDate() returns a Date object.

What is the type of date? A String? A Date object? – nanofarad Aug 18 '13 at 14:36 — nanofarad, Aug 18 '13 at 14:36
what is the expected behaviour for past dates? – Stefan Neubert Aug 18 '13 at 14:39 — Stefan Neubert, Aug 18 '13 at 14:39
the past dates should come last – user1940676 Aug 18 '13 at 14:39 — user1940676, Aug 18 '13 at 14:39

score 5 · Answer 1 · answered Aug 18 '13 at 14:40

5

Create today's date outside the comparator, and change your comparator to compare absolute differences for the dates it compares, like this:

final long todayTime = new Date().getTime();
Collections.sort(unsortedDates, new Comparator<Item>() {
    public int compare(Item m1, Item m2) {
        long dist1 = Math.abs(todayTime-m1.getDate().getTime());
        long dist2 = Math.abs(todayTime-m2.getDate().getTime());
        return Long.compare(dist1, dist2);
    }
});

answered Aug 18 '13 at 14:40

Sergey Kalinichenko

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It sorts the dates so the first date is 12/12 and the last date is 1/1. – user1940676 Aug 18 '13 at 15:07
@user1940676 Swap `dist1` and `dist2` in the call of `Long.compare` to reverse the order. – Sergey Kalinichenko Aug 18 '13 at 15:08
It still does not start from 8/18 , but from 1/1. – user1940676 Aug 18 '13 at 15:11
@user1940676 Then it must be the `1/1` of a different year. Do you want the year portion ignored? – Sergey Kalinichenko Aug 18 '13 at 15:18

score 3 · Answer 2 · answered Aug 18 '13 at 14:41

Code for Java 1.5+ (autoboxing).

final long current = (new Date()).getTime();
Collections.sort(unsortedDates, new Comparator<Item>() {
    public int compare(Item m1, Item m2) {
        Long m1diff = Math.abs(m1.getDate().getTime() - current);
        Long m2diff = Math.abs(m2.getDate().getTime() - current);
        return m1diff.compareTo(m2diff);
    }
});

score 0 · Answer 3 · edited May 23 '17 at 10:25

0

This guy has pretty much the same code as you in his answer. Maybe worth checking out.

Sort a List of Objects by Their Date

Or you have this, but it uses an ArrayList so it may not be what you're looking for, but somewhat similar.

Sort Objects in ArrayList by Date

edited May 23 '17 at 10:25

Community

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answered Aug 18 '13 at 14:41

Watercolours

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Sort List by dates when the first date is today

3 Answers3