ArrayList elements as Map key?

Question

Java

There is an ArrayList < `Character > list, there is a HashMap<Character, Integer> map
Why does the compiler in map.put(list[i], 0) swear at list[i] in the loop? At the same time, if you convert to an array char[ ] arrayChar = list.toArray(), then map.put(arrayChar[i], 0) does not cause problems.

Answer 1

Looks like you need to write map.put(list.get(i), 0)