android - reverse the order of an array

Question

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.

Answer 1

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));
                }

Answer 2

You can do this in two steps:

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

Answer 3

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)

Answer 4

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)}