java - Empty an ArrayList or just create a new one and let the old one be garbage collected?

Question

(This question already has answers here): question from:https://stackoverflow.com/questions/18370780/empty-an-arraylist-or-just-create-a-new-one-and-let-the-old-one-be-garbage-colle

Answer 1

You keep the container and call clear when you would like to reduce the load on GC: clear() nulls out all the references inside the array, but does not make the array eligible for reclaiming by the garbage collector. This may speed up future inserts, because the array inside ArrayList does not need to grow. This approach is especially advantageous when the data that you plan to add to the container has roughly the same size as you clearing out.

In addition, you may need to use clear when other objects hold a reference to the array that you are about to clear.

Releasing the container and creating a new one makes sense when the size of the new data may be different from what was there before. Of course you can achieve a similar effect by calling clear() in combination with trimToSize().