CODEWITHSUNDEEP
androidarraysreverse
user401183
user401183

Reputation: 2570

android - reverse the order of an array

I have an array of objects.

Is it possible to make a new array that is a copy of this array, but in reverse order? I was looking for something like this. 

// my array
ArrayList<Element> mElements = new ArrayList<Element>();
// new array
ArrayList<Element> tempElements = mElements;

tempElements.reverse(); // something to reverse the order of the array

Upvotes: 62

Views: 54712

Answers (5)

Kishan Solanki
Kishan Solanki

Reputation: 14618

Kotlin

val reverseList: List<Int> = yourActualList.reversed();

Reference

Upvotes: 3

hitesh
hitesh

Reputation: 378

I reversed the Profile from ascending to descending order by

In kotlin

 // A comparator to compare points of Profile 
class ProfileComparator {
    companion object : Comparator<Profile?> {
        override fun compare(o1: Profile?, o2: Profile?): Int {
            if (o1 == null || o2 == null) {
                return 0;
            }
            return o2.points.compareTo(o1.points)
        }
    }
}

and then

var profilesList = profiles.sortedWith(ProfileComparator)

Upvotes: 0

DarkCygnus
DarkCygnus

Reputation: 7838

For Android on Kotlin, this can be done with Anko's forEachReversedByIndex{} lambda operation, like this:

val tempElements = ArrayList<Element>(mElements.size)
mElements.forEachReversedByIndex{tempElements.add(it)}

Upvotes: 0

Samir
Samir

Reputation: 6605

Simple approach without implementing anything.

                ArrayList<YourObject> oldlist = new ArrayList<YourObject>();
                ArrayList<YourObject> newList = new ArrayList<YourObject>();
                int size = oldlist.size()-1;

                for(int i=size;i>=0;i--){
                    newList.add(oldlist.get(i));
                }

Upvotes: 0

Ted Hopp
Ted Hopp

Reputation: 234795

You can do this in two steps:

ArrayList<Element> tempElements = new ArrayList<Element>(mElements);
Collections.reverse(tempElements);

Upvotes: 231

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