feat:W6

W6/Animal.java

@@ -0,0 +1,5 @@
+package W6;
+
+public abstract class Animal {
+    public abstract void makeSound();
+}

W6/AnimalTest.java

@@ -0,0 +1,13 @@
+package W6;
+
+public class AnimalTest {
+    public static void main(String args[]){
+        Animal dog=new Dog;
+        Animal cat=new Cat;
+        dog.makeSound();
+        cat.makeSound();
+        if (dog instanceof Swimmable){
+            ((Swimmable)dog).swim();
+        }
+    }
+}

W6/Cat.java

@@ -0,0 +1,8 @@
+package W6;
+
+public class Cat extends Animal{
+    @Override
+    public void makeSound(){
+        System.out.println("喵喵喵");
+    }
+}

W6/Dog.java

@@ -0,0 +1,12 @@
+package W6;
+
+public class Dog extends Animal implements Swimmable{
+    @Override
+    public void makeSound(){
+        System.out.println("汪汪汪");
+    }
+    @Override
+    public void swim(){
+        System.out.println("狗会游泳");
+    }
+}

W6/Swimmable.java

@@ -0,0 +1,5 @@
+package W6;
+
+public interface Swimmable {
+    void swim();
+}