diff --git a/day10/src/com/inmind/duotai08/interface_duotai/Demo12.java b/day10/src/com/inmind/duotai08/interface_duotai/Demo12.java
new file mode 100644
index 0000000..c96fd50
--- /dev/null
+++ b/day10/src/com/inmind/duotai08/interface_duotai/Demo12.java
@@ -0,0 +1,23 @@
+package com.inmind.duotai08.interface_duotai;
+/*
+接口和实现类的多态
+
+多态的前提：
+1.继承或实现
+2.重写
+3.父类引用指向子类对象
+ */
+public class Demo12 {
+    public static void main(String[] args) {
+        MyInterfaceImpl myInterface = new MyInterfaceImpl();//是不是多态？？？不是
+        //多态的格式：父类引用指向子类对象
+        //接口中的多态格式：接口类型 对象名 = new 实现类类型();
+        MyInterface myInterface1 = new MyInterfaceImpl();//多态的写法,向上转型
+        myInterface1.show();//编译看左边，运行看右边
+        //但是我就想要调用实现类的show1方法，那怎么办？？？
+        if (myInterface1 instanceof MyInterfaceImpl) {//为了类型转换时，避免出现类型转换异常，先判断类型
+            MyInterfaceImpl m = (MyInterfaceImpl)myInterface1; //向下转型
+            m.show1();
+        }
+    }
+}
diff --git a/day10/src/com/inmind/duotai08/interface_duotai/MyInterface.java b/day10/src/com/inmind/duotai08/interface_duotai/MyInterface.java
new file mode 100644
index 0000000..95a8740
--- /dev/null
+++ b/day10/src/com/inmind/duotai08/interface_duotai/MyInterface.java
@@ -0,0 +1,5 @@
+package com.inmind.duotai08.interface_duotai;
+
+public interface MyInterface {
+    public abstract void show();
+}
diff --git a/day10/src/com/inmind/duotai08/interface_duotai/MyInterfaceImpl.java b/day10/src/com/inmind/duotai08/interface_duotai/MyInterfaceImpl.java
new file mode 100644
index 0000000..bdcd59a
--- /dev/null
+++ b/day10/src/com/inmind/duotai08/interface_duotai/MyInterfaceImpl.java
@@ -0,0 +1,13 @@
+package com.inmind.duotai08.interface_duotai;
+
+public class MyInterfaceImpl implements MyInterface{
+    @Override
+    public void show() {
+        System.out.println("实现类的show方法");
+    }
+
+
+    public void show1() {
+        System.out.println("实现类的show1方法");
+    }
+}