diff --git a/ StringReverse.java b/ StringReverse.java
deleted file mode 100644
index b394a67..0000000
--- a/ StringReverse.java	
+++ /dev/null
@@ -1,17 +0,0 @@
-public class StringReverse {
-    // 字符串反转 数组双指针解法
-    // String无法直接操作内部的char数组，避免不了2倍内存开销
-    public static void main(String[] args) {
-        String str = "1234567";
-        char[] chars = str.toCharArray();
-        int len = chars.length;
-        char x, y;
-        for (int index = 0, mid = len >> 1, end = len - 1; index < mid; index++, end--) {
-            x = chars[index];
-            y = chars[end];
-            chars[index] = y;
-            chars[end] = x;
-        }
-        System.out.println(new String(chars));
-    }
-}
diff --git a/ArrayReverse.java b/ArrayReverse.java
deleted file mode 100644
index 7c7fc99..0000000
--- a/ArrayReverse.java
+++ /dev/null
@@ -1,21 +0,0 @@
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.List;
-
-public class ArrayReverse {
-    // ArrayList 反转元素
-    // 双指针解法
-    // 出自 java.util.Collections#reverse
-    public static void main(String[] args) {
-        List<Integer> list = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5, 6, 7));
-        int size = list.size();
-        Integer x, y;
-        for (int begin = 0, mid = size >> 1, end = size - 1; begin < mid; begin++, end--) {
-            x = list.get(begin);
-            y = list.get(end);
-            list.set(begin, y);
-            list.set(end, x);
-        }
-        System.out.println(list);
-    }
-}
diff --git a/InOrderTraversal.java b/InOrderTraversal.java
index 88f80f4..18c2c58 100644
--- a/InOrderTraversal.java
+++ b/InOrderTraversal.java
@@ -27,7 +27,7 @@ public class InOrderTraversal {
         TreeNode right;
 
         TreeNode(int x) {
-            val = x;
+            this.val = x;
         }
     }
 
diff --git a/ReverseElements.java b/ReverseElements.java
new file mode 100644
index 0000000..7776a0a
--- /dev/null
+++ b/ReverseElements.java
@@ -0,0 +1,36 @@
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+public class ReverseElements {
+    
+    // 双指针 ArrayList 反转元素 出自 java.util.Collections#reverse
+    public static void array() {
+        List<Integer> list = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5, 6, 7));
+        int size = list.size();
+        Integer x, y;
+        for (int begin = 0, mid = size >> 1, end = size - 1; begin < mid; begin++, end--) {
+            x = list.get(begin);
+            y = list.get(end);
+            list.set(begin, y);
+            list.set(end, x);
+        }
+        System.out.println(list);
+    }
+
+    // 双指针反转字符串 String无法直接操作内部的char数组 避免不了2倍内存开销
+    public static void main(String[] args) {
+        String str = "1234567";
+        char[] chars = str.toCharArray();
+        int len = chars.length;
+        char x, y;
+        for (int index = 0, mid = len >> 1, end = len - 1; index < mid; index++, end--) {
+            x = chars[index];
+            y = chars[end];
+            chars[index] = y;
+            chars[end] = x;
+        }
+        System.out.println(new String(chars));
+    }
+
+}