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.

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

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

Answer 1

You can do this in two steps:

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

Answer 2

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 3

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)}