如何检查char是否出现在ArrayList的字符串中？

问：

我正在写一个刽子手游戏，我需要一种方法来检查玩家输入的字母是否出现在计算机从 ArrayList 中提取的单词中。我需要为此使用流吗？我从未使用过流，但现在可能是时候了。为了更好地理解，我投入了我的代码。对象和字符串是波兰语。我想放在 createCipher 类中的方法

import java.util.ArrayList;
import java.util.Random;
import java.util.Scanner;

public class Hangman {
    static ArrayList<String> words = new ArrayList<>();

    public static void main(String[] args) {
        PrepareGame pomocnik = new PrepareGame();
        PrepareGame.playerChoice pomocnik2 = new PrepareGame.playerChoice();
        words.add("Puszka");
        words.add("Kot");
        words.add("Pies");

        pomocnik.drawWord();
        pomocnik.countLetters();
        pomocnik.createCipher();
        pomocnik2.choose();
    }
}

class PrepareGame {
    playerChoice player = new playerChoice();
    String randomWords;

    void drawWord() {
        Random r = new Random();
        int randomitem = r.nextInt(Hangman.words.size());
        String randomW = Hangman.words.get(randomitem);
        randomWords = randomW;
        System.out.println(randomW);
    }

    void countLetters() {
        int len = randomWords.length();
        System.out.println(len);
    }

    void createCipher() {
            for (int cypher = 0; cypher < randomWords.length(); cypher++) {
                System.out.print("_");
            }
    }

    static class playerChoice {
        ArrayList<String> selectedLetter = new ArrayList<>();
        String choice;
        Scanner scan = new Scanner(System.in);

        void choose() {
            System.out.println(" ");
            System.out.println("wpisz litere: ");
            String pChoice = scan.nextLine();
            choice = pChoice;
            selectedLetter.add(choice);
            System.out.println("Wybrana litera: " + choice);

        }
    }
}

我尝试使用indexOf（）和contains（）但没有成功。也许我用错了。