diff --git a/s-day01/src/com/inmind/StringBuilder07/Demo17.java b/s-day01/src/com/inmind/StringBuilder07/Demo17.java
new file mode 100644
index 0000000..b40dbdd
--- /dev/null
+++ b/s-day01/src/com/inmind/StringBuilder07/Demo17.java
@@ -0,0 +1,23 @@
+package com.inmind.StringBuilder07;
+/*
+    注意：string类的拼接，会导致多余的字符串，就会字符串常量池中占用内存，那么可以使用StringBuilder来解决
+ */
+public class Demo17 {
+    public static void main(String[] args) {
+        String str1 = "hello";
+        String str2 = "java";
+        String str3 = "world";
+        /*
+        这样写字符串对象有几个？？？*/
+        System.out.println(str1+str2+str3);//产生了5个字符串对象
+
+        //StringBuilder可以优化以上代码的,这里只产生了4个字符串对象
+        StringBuilder sb = new StringBuilder();
+        sb = sb.append(str1).append(str2).append(str3);
+        System.out.println(sb);
+        String str4 = sb.toString();
+        System.out.println(str4);
+
+
+    }
+}