See the difference? Arrays.asList and Collections.toArray
So the Arrays.asList-method is not copying an array into a new list, it gives you just a new List-view on the array. As an array-Object is of fixed size (3 elements in this case) you are not able to add a fourth element into it, neither delete one to get an array of size two. If you are not allowed to do these operations on the array, you are of course not allowed to do the same things to your List-view, as these changes would write through to the array. Hope, that helps.