// 统一支付接口
interface PaymentGateway {
    void pay(double amount);
}

// 旧版支付系统（需适配）
class LegacyPaySystem {
    void executeLegacyPayment(String currency, double value) {
        System.out.println("Processing legacy payment: " + value + " " + currency);
    }
}

// 适配器类
class PaymentAdapter implements PaymentGateway {
    private LegacyPaySystem legacySystem;

    public PaymentAdapter(LegacyPaySystem system) {
        this.legacySystem = system;
    }

    @Override
    public void pay(double amount) {
        legacySystem.executeLegacyPayment("USD", amount); // 硬编码货币为USD
    }
}

// 客户端使用
public class BasicPaymentAdapter {
    public static void main(String[] args) {
        PaymentGateway gateway = new PaymentAdapter(new LegacyPaySystem());
        gateway.pay(199.99); // 统一接口调用
    }
}