chapter 4

src/chapter4/example10/Example10.java

@@ -0,0 +1,19 @@
+package chapter4.example10;
+
+abstract class Animal {
+    abstract void shout();
+
+}
+
+class Dog extends Animal {
+    void shout() {
+        System.out.println("汪汪...");
+    }
+}
+
+public class Example10 {
+    public static void main(String[] args) {
+        Animal dog = new Dog();
+        dog.shout();
+    }
+}