IndexOutOfBoundsException when adding to ArrayList at index

Question

I get exception Exception in thread \"main\" java.lang.IndexOutOfBoundsException: Index: 1, Size: 0 for the below code. But couldn\'t understand why.

Answer 1

By the way, ArrayList s = new ArrayList<>(10); set the initialCapacity to 10.

Since the capacity of Arraylist is adjustable, it only makes the java knows the approximate capacity and try to avoid the performance loss caused by the capacity expansion.