Why isn't this working?

Question

Why is my code producing error and how to correct it while doing the same thing I wanted to do(covering an ArrayList to array)?
https://code.sololearn.com/cfzT5YYlTatb/?ref=app

Answer 1

Line 21 :
Test[] arr=al.toArray(new Test[0]);

Answer 2

Flash okay I guess it's the size of the array. I fixed my code as below:

https://code.sololearn.com/ccxQrmG8GBh7/?ref=app

Tnx again for your help =)

Answer 3

Flash Tnx, but what does that 0 mean in "new Test[0]"?