diff --git a/w6/AnimalSystem.java b/w6/AnimalSystem.java
new file mode 100644
index 0000000..dbc005c
--- /dev/null
+++ b/w6/AnimalSystem.java
@@ -0,0 +1,41 @@
+abstract class Animal {
+    public abstract void makeSound();
+}
+interface Swimmable {
+    void swim();
+}
+class Dog extends Animal implements Swimmable {
+    @Override
+    public void makeSound() {
+        System.out.println("小狗汪汪叫");
+    }
+    @Override
+    public void swim() {
+        System.out.println("小狗会游泳");
+    }
+}
+class Cat extends Animal {
+    @Override
+    public void makeSound() {
+        System.out.println("小猫喵喵叫");
+    }
+}
+public class AnimalSystem {
+    public static void main(String[] args) {
+        Animal animal1 = new Dog();
+        Animal animal2 = new Cat();
+        animal1.makeSound();
+        animal2.makeSound();
+        System.out.println("-------------------");
+        if (animal1 instanceof Swimmable) {
+            Swimmable swimmer = (Swimmable) animal1;
+            swimmer.swim();
+        }
+        if (animal2 instanceof Swimmable) {
+            Swimmable swimmer = (Swimmable) animal2;
+            swimmer.swim();
+        } else {
+            System.out.println("小猫不会游泳");
+        }
+    }
+}
\ No newline at end of file