There are some problems with your code :
1. On Arrays.asList executing a fixed-size list
Arrays.asList: Returns a fixed-size list backed by the specified array.
This means that you can not add to it; you can not remove from it. You can not structurally alter the List.
Build a LinkedList, which promotes faster remove.
List<String> list = new LinkedList<String>(Arrays.asList(split));
2. On split taking regex
String.split(String regex): Splits this string around matches of the given regular expression.
| is a regex metacharacter; if you require to break on a literal |, you need to avoid it to \|, which as a Java string literal is "\\|".
Alternatively, Rather than calling remove one at a time with arbitrary indices, it's more satisfying to create enough random numbers in the range, and then crossing the List once with a listIterator(), calling remove() at relevant indices.
By this, your algorithm would be O(N).
Hope this helps…!!