diff --git a/day09/src/com/inmind/abstract_test07/Circle.java b/day09/src/com/inmind/abstract_test07/Circle.java
new file mode 100644
index 0000000..6d5ede1
--- /dev/null
+++ b/day09/src/com/inmind/abstract_test07/Circle.java
@@ -0,0 +1,19 @@
+package com.inmind.abstract_test07;
+
+public class Circle extends Shape {
+
+    //创建圆必定要半径
+    public Circle(int r){
+        super(0,0,r);
+    }
+
+    @Override
+    public int getArea() {
+        return (int)(Math.PI*getR()*getR());
+    }
+
+    @Override
+    public int getZC() {
+        return (int)(2*Math.PI*getR());
+    }
+}
diff --git a/day09/src/com/inmind/abstract_test07/Demo11.java b/day09/src/com/inmind/abstract_test07/Demo11.java
index 26ea505..3c4b8cc 100644
--- a/day09/src/com/inmind/abstract_test07/Demo11.java
+++ b/day09/src/com/inmind/abstract_test07/Demo11.java
@@ -1,6 +1,8 @@
 package com.inmind.abstract_test07;
 /*
 简单练习：定义一个图形类，求周长和面积，但是有不知道如何实现，只能由具体的图形子类(长方形，圆形)实现
+
+练习：定义一个圆类，参照长方形类来实现！！！(Math.PI)
  */
 public class Demo11 {
     public static void main(String[] args) {
@@ -8,5 +10,15 @@ public class Demo11 {
         Rectangle rectangle = new Rectangle(4, 3);
         System.out.println("长方形面积为："+rectangle.getArea());
         System.out.println("长方形周长为："+rectangle.getZC());
+        //创建一个圆形
+        Circle circle = new Circle(2);
+        System.out.println("圆形面积为："+circle.getArea());
+        System.out.println("圆形周长为："+circle.getZC());
+        //如何快速定义出一个正方形的类，还不用自己实现周长和面积的方法
+        // (注意：正方形是一种特殊的长方形)
+        Square square = new Square(4);
+        System.out.println("正方形面积为："+square.getArea());
+        System.out.println("正方形周长为："+square.getZC());
+
     }
 }
diff --git a/day09/src/com/inmind/abstract_test07/Square.java b/day09/src/com/inmind/abstract_test07/Square.java
new file mode 100644
index 0000000..54595de
--- /dev/null
+++ b/day09/src/com/inmind/abstract_test07/Square.java
@@ -0,0 +1,8 @@
+package com.inmind.abstract_test07;
+
+public class Square extends Rectangle{
+    //在创建正方形对象，必须传入1个属性：边长
+    public Square(int bc){
+        super(bc,bc);
+    }
+}