diff --git a/.idea/GitCommitMessageStorage.xml b/.idea/GitCommitMessageStorage.xml
new file mode 100644
index 0000000..e4fd56a
--- /dev/null
+++ b/.idea/GitCommitMessageStorage.xml
@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="GitCommitMessageStorage">
+    <option name="messageStorage">
+      <MessageStorage />
+    </option>
+  </component>
+</project>
\ No newline at end of file
diff --git a/demo1/src/main/java/cn/bunny/Demo4.java b/demo1/src/main/java/cn/bunny/Demo4.java
new file mode 100644
index 0000000..dfc828b
--- /dev/null
+++ b/demo1/src/main/java/cn/bunny/Demo4.java
@@ -0,0 +1,20 @@
+package cn.bunny;
+
+import java.nio.ByteBuffer;
+
+public class Demo4 {
+    public static void main(String[] args) {
+        ByteBuffer buffer = ByteBuffer.allocate(10);
+        buffer.put(new byte[]{'a', 'b', 'c', 'd', 'e'});
+
+        // rewind 重头开始读
+        buffer.get(new byte[4]);
+        // 重新读取
+        buffer.rewind();
+        System.out.println((char) buffer.get());// a
+
+        // mark & reset
+        System.out.println((char) buffer.get());// b
+        System.out.println((char) buffer.get());// c
+    }
+}
diff --git a/demo1/target/classes/cn/bunny/Demo4.class b/demo1/target/classes/cn/bunny/Demo4.class
new file mode 100644
index 0000000..2504098
Binary files /dev/null and b/demo1/target/classes/cn/bunny/Demo4.class differ