ADD file via upload

BasicPaymentAdapter.java

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+// 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
+    }
+}