在Java项目里如何正确使用接口_接口驱动开发的设计模式示例

public interface PaymentService {
    <strong>boolean pay(double amount);</strong>
    String getPaymentMethod();
}

public class AlipayServiceImpl implements PaymentService {
    public boolean pay(double amount) {
        System.out.println("使用支付宝支付: " + amount + "元");
        return true; // 模拟成功
    }

    public String getPaymentMethod() {
        return "Alipay";
    }
}

public class WechatPayServiceImpl implements PaymentService {
    public boolean pay(double amount) {
        System.out.println("使用微信支付: " + amount + "元");
        return true;
    }

    public String getPaymentMethod() {
        return "WeChat";
    }
}

public class OrderService {

    private final PaymentService paymentService;

    public OrderService(PaymentService paymentService) {
        this.paymentService = paymentService;
    }

    public void checkout(double amount) {
        System.out.println("订单金额: " + amount);
        if (paymentService.pay(amount)) {
            System.out.println("支付成功！");
        } else {
            System.out.println("支付失败！");
        }
    }
}

// 用户选择支付宝
PaymentService alipay = new AlipayServiceImpl();
OrderService orderService = new OrderService(alipay);
orderService.checkout(299.9);

// 切换为微信支付，无需修改OrderService
PaymentService wechat = new WechatPayServiceImpl();
OrderService wechatOrder = new OrderService(wechat);
wechatOrder.checkout(199.0);

public class PaymentFactory {
    public static PaymentService getPayment(String method) {
        switch (method.toLowerCase()) {
            case "alipay":  return new AlipayServiceImpl();
            case "wechat":  return new WechatPayServiceImpl();
            default: throw new IllegalArgumentException("不支持的支付方式");
        }
    }
}

String userChoice = "alipay";
PaymentService service = PaymentFactory.getPayment(userChoice);
new OrderService(service).checkout(99.5);