Sort List in reverse in order

Question

I have List list1 in direct order. List<String> list = Ordering.natural().sortedCopy(asu2);

How to change order. And I don't know how to rewrite methods from extends class, please write with examples or speak clearly.

What exactly to you mean by "change order"? Reverse the list or apply a completely new order to it based on a specific ruleset? — f1sh, Aug 06 '13 at 07:01
You want the list to be sorted in the descending order. Right? — JHS, Aug 06 '13 at 07:03
@EldarNezametdinov - I answered your question to get a simple descending order. — JHS, Aug 06 '13 at 07:12

score 121 · Answer 1 · answered Aug 06 '13 at 07:01

121

Use this:

Collections.reverse(list);

answered Aug 06 '13 at 07:01

morgano

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7

Does this sort in the descending order or just reverse the order in which the elements were inserted? – JHS Aug 06 '13 at 07:13
5

It just reverse the order elements. – Eldar Nezametdinov Aug 06 '13 at 07:47
7

This answer is misleading. It doesn't sort a collection in descending order - merely switches last element with first, second to last with second, etc – parsecer Jun 26 '20 at 00:26
The question in misleading, if the intent was to just reverse the list, this will work. – Akhil Mar 08 '21 at 18:16

score 59 · Answer 2 · answered Aug 06 '13 at 07:01

59

There is a method reverseOrder in the Collections class which returns a Comparator.

You can use it like Collections.sort(list, Collections.reverseOrder());

answered Aug 06 '13 at 07:01

JHS

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I would consider your answer, since it would not be necessary to arrange for only after reverting. Your approach is capable of performing two operations in a single frame. I don't know about the others, but thank you. – Loa Mar 26 '17 at 20:20
2

Or just `list.sort(Collections.reverseOrder());` – T77 Jul 07 '22 at 00:32

score 41 · Accepted Answer · answered May 30 '19 at 11:27

41

How I would do it is:

personsList.sort(Comparator.comparing(Person::getAge, Comparator.reverseOrder()));

And happy coding :)

answered May 30 '19 at 11:27

panayot_kulchev_bg

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It should've been selected as an answer. this is exactly what I've been looking for. – Masuri Oct 07 '21 at 15:05

score 18 · Answer 4 · edited Mar 21 '17 at 09:51

18

you can reverse any type by just putting "-" or negative sign infront of your return.

Collections.sort(listed, new Comparator<Object>() {

    @Override
    public int compare(Object o1, Object o2) {

        return -o1.getLeft().compareTo(o2.getLeft());

    }
});

edited Mar 21 '17 at 09:51

SymbolixAU

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answered Jun 01 '16 at 02:08

Fikreselam Elala

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And lets hope that `compareTo` will never return minimal integer because `-Integer.MIN_VALUE` is still `Integer.MIN_VALUE`. Safest way would be swapping o1 with o2 like `return o2.getLeft().compareTo(o1.getLeft())` – Pshemo Sep 29 '17 at 21:31

score 8 · Answer 5 · answered Aug 06 '13 at 15:47

8

If you want to sort the list in reverse natural order, guava's Ordering has a reverse method:

List<String> list = Ordering.natural().reverse().sortedCopy(asu2);

answered Aug 06 '13 at 15:47

assylias

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score 3 · Answer 6 · edited May 04 '16 at 09:12

3

To reverse the order of items in List you can use Collections.reverse(List<?> list)

edited May 04 '16 at 09:12

Aritz

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answered Aug 06 '13 at 07:02

Damian Leszczyński - Vash

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score 1 · Answer 7 · answered Aug 06 '13 at 18:37

Collections.reverse(List) reverses the given list in place. You can also use Guava's Lists.reverse(List) to create a view backed by the given list that is in reverse order without copying it or modifying the original list.

And if you just want to create a list that is sorted in the reverse of the natural order, see @assylias's answer about Ordering.natural().reverse().

score 1 · Answer 8 · answered Jul 25 '22 at 08:25

1

Try this neater approach:

Collections.reverseOrder(
  Comparator.comparing(
    MyEntity::getAFieldToSortBy)));

answered Jul 25 '22 at 08:25

Zon

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score 0 · Answer 9 · answered Oct 26 '20 at 18:11

0

list.sort(Comparator.reverseOrder());

answered Oct 26 '20 at 18:11

Alex G

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Sort List in reverse in order

9 Answers9

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