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.

Solution 1

Use this:

Collections.reverse(list);

Solution 2

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

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

Solution 3

How I would do it is:

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

And happy coding :)

Solution 4

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());

    }
});

Solution 5

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);

View more solutions

Comments

[JHS]

Does this sort in the descending order or just reverse the order in which the elements were inserted?

[Eldar Nezametdinov]

It just reverse the order elements.

[Loa]

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.

[Pshemo]

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())

[parsecer]

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

[Akhil]

The question in misleading, if the intent was to just reverse the list, this will work.

[Masuri]

It should've been selected as an answer. this is exactly what I've been looking for.

[T77]

Or just list.sort(Collections.reverseOrder());