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

Solution 1

You can do this in two steps:

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

Solution 2

Kotlin

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

Reference

Comments

[Matthew Willis]

Yikes, thanks Ted. Looks like I have some java.util.* reading to do.

[Ted Hopp]

An improvement would be to create tempElements with an initial capacity at least equal to the size of mElements. That would avoid internal memory reallocations as elements are added in the second line.

[Ted Hopp]

An improvement would be to create newList with an initial capacity at least equal to the size of oldList. That would avoid internal memory reallocations as elements are added in the loop.

[DarkCygnus]

@TedHopp thanks for the suggestion, will see to incorporate it to the answer :)