用Java语言设计一个21点游戏，要求玩家与Al对抗，双方都能看到对方明牌，不考虑庄家和闲家，加倍等情况

以下是一个简单的21点游戏的Java代码实现，双方玩家和AI都能看到对方明牌：

import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;

public class BlackjackGame {

    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);
        System.out.println("欢迎来玩21点游戏！");

        // 创建一副52张的扑克牌
        ArrayList<String> deck = new ArrayList<>();
        String[] suits = {"♠️", "♥️", "♣️", "♦️"};
        String[] ranks = {"A", "2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K"};
        for (String suit : suits) {
            for (String rank : ranks) {
                deck.add(rank + suit);
            }
        }

        // 洗牌
        Collections.shuffle(deck);

        // 初始化玩家和AI的手牌
        ArrayList<String> playerHand = new ArrayList<>();
        ArrayList<String> aiHand = new ArrayList<>();

        // 发牌
        for (int i = 0; i < 2; i++) {
            playerHand.add(deck.remove(0));
            aiHand.add(deck.remove(0));
        }

        // 显示玩家和AI的手牌
        System.out.println("你的手牌：" + playerHand);
        System.out.println("AI的手牌：" + aiHand.get(0) + " 和一张暗牌");

        // 玩家回合
        while (true) {
            System.out.println("请选择：1.要牌 2.停牌");
            int choice = scanner.nextInt();
            if (choice == 1) {
                playerHand.add(deck.remove(0));
                System.out.println("你的手牌：" + playerHand);
                int playerTotal = getTotal(playerHand);
                if (playerTotal > 21) {
                    System.out.println("你爆了！");
                    break;
                }
            } else {
                break;
            }
        }

        // AI回合
        while (getTotal(aiHand) < 17) {
            aiHand.add(deck.remove(0));
            System.out.println("AI的手牌：" + aiHand);
        }

        // 判断胜负
        int playerTotal = getTotal(playerHand);
        int aiTotal = getTotal(aiHand);
        if (playerTotal > 21) {
            System.out.println("AI赢了！");
        } else if (aiTotal > 21) {
            System.out.println("你赢了！");
        } else if (playerTotal > aiTotal) {
            System.out.println("你赢了！");
        } else if (aiTotal > playerTotal) {
            System.out.println("AI赢了！");
        } else {
            System.out.println("平局！");
        }

    }

    // 计算手牌点数
    public static int getTotal(ArrayList<String> hand) {
        int total = 0;
        int aceCount = 0;
        for (String card : hand) {
            String rank = card.substring(0, card.length() - 1);
            if (rank.equals("A")) {
                aceCount++;
            } else if (rank.equals("J") || rank.equals("Q") || rank.equals("K")) {
                total += 10;
            } else {
                total += Integer.parseInt(rank);
            }
        }
        for (int i = 0; i < aceCount; i++) {
            if (total + 11 > 21) {
                total += 1;
            } else {
                total += 11;
            }
        }
        return total;
    }

}

上面的代码使用了ArrayList来表示扑克牌和手牌，使用了Collections的shuffle方法来洗牌，使用了Scanner来获取玩家的选择。在计算手牌点数时，特别处理了A牌的情况。