Лист символов в строку

public static void main(String[] args) {
        List<Character> characterList1 = new ArrayList<>();
        List<Character> characterList2 = new ArrayList<>();
        if (characterList1.size() > characterList2.size()){
            List<Character> character = characterList1;
            characterList1 = characterList2;
            characterList2 = character;
        }
        StringBuilder stringBuilder = new StringBuilder();
        for (int i = 0; i < characterList1.size(); i++) {
            stringBuilder.append(characterList1.get(i));
            stringBuilder.append(characterList2.get(i));
        }
        for (int i = characterList1.size(); i < characterList2.size(); i++) {
            stringBuilder.append(characterList2.get(i));
        }
        String str = stringBuilder.toString();
    }