update:demo4

com/study/demo4/BikeDeliveryCalculator.java

@@ -0,0 +1,11 @@
+package com.study.demo4;
+
+class BikeDeliveryCalculator implements DeliveryFeeCalculator {
+  @Override
+  public double calculateFee(double distance) {
+    if (distance <= 5) {
+      return 5.0; // 起步价
+    }
+    return 5.0 + (distance - 5) * 1.5;
+  }
+}