diff --git a/day08/src/com/inmind/math04/MathDemo11.java b/day08/src/com/inmind/math04/MathDemo11.java
index f472da6..5514a7f 100644
--- a/day08/src/com/inmind/math04/MathDemo11.java
+++ b/day08/src/com/inmind/math04/MathDemo11.java
@@ -7,6 +7,7 @@ public static double floor(double a) ：返回小于等于参数最大的整数
 public static long round(double a) ：返回最接近参数的 long。(相当于四舍五入方法)
  */
 public class MathDemo11 {
+
     public static void main(String[] args) {
 
         //获取绝对值
@@ -19,4 +20,9 @@ public class MathDemo11 {
         System.out.println(Math.round(4.4));//4
         System.out.println(Math.round(4.5));//5
     }
+
+    public  void methos() {
+        System.out.println(Math.round(4.4));//4
+        System.out.println(Math.round(4.5));//5
+    }
 }
diff --git a/day09/day09.iml b/day09/day09.iml
new file mode 100644
index 0000000..6db0c46
--- /dev/null
+++ b/day09/day09.iml
@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module type="JAVA_MODULE" version="4">
+  <component name="NewModuleRootManager" inherit-compiler-output="true">
+    <exclude-output />
+    <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
+    </content>
+    <orderEntry type="jdk" jdkName="17" jdkType="JavaSDK" />
+    <orderEntry type="sourceFolder" forTests="false" />
+  </component>
+</module>
\ No newline at end of file
diff --git a/day09/src/com/inmind/extends01/Assistant.java b/day09/src/com/inmind/extends01/Assistant.java
new file mode 100644
index 0000000..1ea5446
--- /dev/null
+++ b/day09/src/com/inmind/extends01/Assistant.java
@@ -0,0 +1,8 @@
+package com.inmind.extends01;
+
+public class Assistant extends Employee {
+
+    public void help(){
+        System.out.println("助教在帮助学生");
+    }
+}
diff --git a/day09/src/com/inmind/extends01/BanZhuRen.java b/day09/src/com/inmind/extends01/BanZhuRen.java
new file mode 100644
index 0000000..5761675
--- /dev/null
+++ b/day09/src/com/inmind/extends01/BanZhuRen.java
@@ -0,0 +1,8 @@
+package com.inmind.extends01;
+
+public class BanZhuRen extends Employee {
+
+    public void manage(){
+        System.out.println("班主任在管理学生");
+    }
+}
diff --git a/day09/src/com/inmind/extends01/Demo01.java b/day09/src/com/inmind/extends01/Demo01.java
new file mode 100644
index 0000000..5683355
--- /dev/null
+++ b/day09/src/com/inmind/extends01/Demo01.java
@@ -0,0 +1,23 @@
+package com.inmind.extends01;
+/*
+继承的格式和和基本使用
+public class Fu{
+}
+public class Zi extends Fu{
+}
+继承的特点：子类拥有父类的所有内容，除了被private和构造方法。
+继承的好处：实现多个类中相同内容的复用,子类可以实现各自的不同功能需求
+ */
+public class Demo01 {
+    public static void main(String[] args) {
+        //创建一个子类对象，老师对象
+        Teacher t = new Teacher();
+        t.name = "张三";
+        t.age = 35;
+        t.salary = 1.5;
+        t.work();
+        t.teach();
+        Assistant a = new Assistant();
+        a.help();
+    }
+}
diff --git a/day09/src/com/inmind/extends01/Employee.java b/day09/src/com/inmind/extends01/Employee.java
new file mode 100644
index 0000000..9533c21
--- /dev/null
+++ b/day09/src/com/inmind/extends01/Employee.java
@@ -0,0 +1,11 @@
+package com.inmind.extends01;
+
+public class Employee {
+    String name;
+    int age;
+    double salary;
+
+    public void work(){
+        System.out.println("员工工作了");
+    }
+}
diff --git a/day09/src/com/inmind/extends01/Teacher.java b/day09/src/com/inmind/extends01/Teacher.java
new file mode 100644
index 0000000..6c118f4
--- /dev/null
+++ b/day09/src/com/inmind/extends01/Teacher.java
@@ -0,0 +1,9 @@
+package com.inmind.extends01;
+
+public class Teacher extends Employee{
+    //默认无参构造，所有类都有构造方法
+
+    public void teach(){
+        System.out.println("老师在教学生学java");
+    }
+}