The methods getSystemMnemonicKeyCodes and getKeyCodesFromKeyMask declare ArrayList as the return type. It doesn't have to be a specific type.

I propose replacing ArrayList<Integer> with List<Integer>.

In this case, getSystemMnemonicKeyCodes could return List.of, which would look cleaner.

In addition to that, getKeyCodesFromKeyMask uses the deprecated constants, replace these constants with their alternatives.