diff --git a/lecture/src/lecture4_3.java b/lecture/src/lecture4_3.java
index 398a052..309e3c4 100644
--- a/lecture/src/lecture4_3.java
+++ b/lecture/src/lecture4_3.java
@@ -28,8 +28,6 @@ public static Dog max(Dog[] items){
 
     public static void getWords(String inputFileName){
         List<String> lst = new ArrayList<String>();
-        In in = new In();
-        
     }
 }
 
diff --git a/lecture/src/lecutre4_1.java b/lecture/src/lecutre4_1.java
index 9124655..fdf1776 100644
--- a/lecture/src/lecutre4_1.java
+++ b/lecture/src/lecutre4_1.java
@@ -27,5 +27,44 @@ public static String smallest(SList<String> input){
     }
 }
 
+class SLList<Item> implements List61B<Item>{
+
+    @Override
+    public void addFirst(Item x) {
+    }
+
+    @Override
+    public void addLast(Item y) {
+    }
+
+    @Override
+    public Item getFirst() {
+        return null;
+    }
+
+    @Override
+    public Item getLast() {
+        return null;
+    }
+
+    @Override
+    public Item removeLast() {
+        return null;
+    }
+
+    @Override
+    public Item get(int i) {
+        return null;
+    }
+
+    @Override
+    public void insert(Item x, int position) {
+    }
+
+    @Override
+    public int size() {
+        return 0;
+    }
+}
 
 
diff --git a/lecture_4.md b/lecture_4.md
index d57ef60..dfda410 100644
--- a/lecture_4.md
+++ b/lecture_4.md
@@ -239,7 +239,7 @@ public static void main(String[] args) {
 
 试想一下，一旦有很多子类，那么这个工作量将会比没有使用向上转型大很多。这也表明向上转型还有个优点就是提高了代码的简洁性。
 
-**重点：经过向上转型之后，在利用.操作符访问时，如果访问的是对象的属性，则编译的话就是看父类，运行同样是看父类；如果访问的是方法，编译就看父类，运行则看子类；如果访问的是父类中表明的static methods，尽管子类已经进行override，但编译和运行都是看父类**
+**重点：经过向上转型之后，在利用.操作符访问时，如果访问的是对象的属性，则编译的话就是看父类，运行同样是看父类；如果访问的是方法，编译就看父类，运行则看子类；如果访问的是父类中标明的static methods，尽管子类已经进行override，但编译和运行都是看父类**
 
 ### High order function(高阶函数，HOF)
 
@@ -377,8 +377,6 @@ Exception in thread "main" java.lang.ClassCastException: class SList cannot be c
 	at lecture4_2.main(lecture4_2.java:14)
 ```
 
-
-
 ### 内置Comparable接口
 
 事实上，java内置的Comparable接口与我们构建的Ourcomparable接口仅有细微的差别，其内置接口定义如下：
diff --git a/lecture_5.md b/lecture_5.md
new file mode 100644
index 0000000..e69de29
diff --git a/out/production/lecture/Benz.class b/out/production/lecture/Benz.class
new file mode 100644
index 0000000..daf6c77
Binary files /dev/null and b/out/production/lecture/Benz.class differ
diff --git a/out/production/lecture/Car.class b/out/production/lecture/Car.class
new file mode 100644
index 0000000..7c89167
Binary files /dev/null and b/out/production/lecture/Car.class differ
diff --git a/out/production/lecture/Dog$NameComparator.class b/out/production/lecture/Dog$NameComparator.class
index 749be26..3b57e71 100644
Binary files a/out/production/lecture/Dog$NameComparator.class and b/out/production/lecture/Dog$NameComparator.class differ
diff --git a/out/production/lecture/Dog.class b/out/production/lecture/Dog.class
index ba2a36b..59e52c4 100644
Binary files a/out/production/lecture/Dog.class and b/out/production/lecture/Dog.class differ
diff --git a/out/production/lecture/SLList.class b/out/production/lecture/SLList.class
new file mode 100644
index 0000000..e6650fd
Binary files /dev/null and b/out/production/lecture/SLList.class differ
diff --git a/out/production/lecture/lecture4_3.class b/out/production/lecture/lecture4_3.class
index 7133fd8..3bfb56b 100644
Binary files a/out/production/lecture/lecture4_3.class and b/out/production/lecture/lecture4_3.class differ
diff --git "a/\346\234\252\345\256\214\346\210\220\347\232\204\344\273\273\345\212\241.md" "b/\346\234\252\345\256\214\346\210\220\347\232\204\344\273\273\345\212\241.md"
index 43d88bb..08ab3a1 100644
--- "a/\346\234\252\345\256\214\346\210\220\347\232\204\344\273\273\345\212\241.md"
+++ "b/\346\234\252\345\256\214\346\210\220\347\232\204\344\273\273\345\212\241.md"
@@ -1,8 +1,6 @@
-# 双向链表（Intnode中的prev指针）（project1 待完成）
+### 双向链表（Intnode中的prev指针）（project1 待完成）
 
-# 你泛型还没有真正弄懂！
+### lecutre 4.4中所有的excerises都没有做！
 
-# 继承与接口实现中java的向上转型与向下转型！
 
-# java静态类型与动态类型（向上转型后**dynamic method selection**，并不适用于overloaded方法）