update:demo4

com/study/demo4/PaymentFactory.java

@@ -0,0 +1,16 @@
+package com.study.demo4;
+
+class PaymentFactory {
+  public static PaymentProcessor getProcessor(String type) {
+    switch (type.toLowerCase()) {
+      case "wechat":
+        return new WechatPayment();
+      case "alipay":
+        return new AlipayPayment();
+      case "card":
+        return new CreditCardPayment();
+      default:
+        throw new IllegalArgumentException("不支持的支付方式");
+    }
+  }
+}