Question

In order convert a List to an array, you need an empty array like following:

List<Foo> fooList;
Foo[] foos = fooList.toArray(new Foo[0]);

I happen to use this code snippet a lot, so instead of creating an empty array every time, I decided to create a static empty array, and use it each time. e.g.

private static Foo[] EMPTY_FOOS = new Foo[0];

List<Foo> fooList;
Foo[] foos = fooList.toArray(EMPTY_FOOS);

Is this worth it or are we looking at a difference of 0.000000000000000000000000000000000000000000000000000001ms?

Answer 1

Actually I believe this is the best performing version:

fooList.toArray(new Foo[fooList.size()]);

This way toArray() always has the exact array and no extra arrays are created. IntelliJ suggests such a refactoring out of the box.