diff --git a/day10/src/com/inmind/duotai_interface11/Demo11.java b/day10/src/com/inmind/duotai_interface11/Demo11.java
new file mode 100644
index 0000000..5890fe5
--- /dev/null
+++ b/day10/src/com/inmind/duotai_interface11/Demo11.java
@@ -0,0 +1,23 @@
+package com.inmind.duotai_interface11;
+
+import com.inmind.object_cast10.Animal;
+import com.inmind.object_cast10.Cat;
+
+/*
+类的多态 ：父类引用指向子类对象
+接口的多态：接口引用指向实现类对象
+ */
+public class Demo11 {
+    public static void main(String[] args) {
+        MyInterfaceImpl myInterfaceImpl = new MyInterfaceImpl();//普通写法
+        Animal animal = new Cat();//向上转型
+        //接口引用指向实现类对象
+        MyInterface myInterface = new MyInterfaceImpl();//接口的多态(接口的向上转型)
+        myInterface.method();//编译看左边，运行看右边
+        if (myInterface instanceof MyInterfaceImpl){//接口的类型判断
+            MyInterfaceImpl impl = (MyInterfaceImpl) myInterface;//接口的向下转型
+            impl.method1();
+        }
+
+    }
+}
diff --git a/day10/src/com/inmind/duotai_interface11/MyInterface.java b/day10/src/com/inmind/duotai_interface11/MyInterface.java
new file mode 100644
index 0000000..4c0a1c0
--- /dev/null
+++ b/day10/src/com/inmind/duotai_interface11/MyInterface.java
@@ -0,0 +1,5 @@
+package com.inmind.duotai_interface11;
+
+public interface MyInterface {
+    void method();
+}
diff --git a/day10/src/com/inmind/duotai_interface11/MyInterfaceImpl.java b/day10/src/com/inmind/duotai_interface11/MyInterfaceImpl.java
new file mode 100644
index 0000000..fc309cc
--- /dev/null
+++ b/day10/src/com/inmind/duotai_interface11/MyInterfaceImpl.java
@@ -0,0 +1,12 @@
+package com.inmind.duotai_interface11;
+
+public class MyInterfaceImpl implements  MyInterface{
+    @Override
+    public void method() {
+        System.out.println("实现类实现了method方法");
+    }
+
+    public void method1(){
+        System.out.println("实现类1中method1方法");
+    }
+}