diff --git a/src/chapter5/Example11.java b/src/chapter5/Example11.java
new file mode 100644
index 0000000..e95df25
--- /dev/null
+++ b/src/chapter5/Example11.java
@@ -0,0 +1,14 @@
+package chapter5;
+
+public class Example11 {
+    public static void main(String[] args) {
+        long startTime = System.currentTimeMillis();
+        String test = "";
+        for (int i = 0; i < 100000; i ++) {
+            test += "test";
+        }
+
+        long endTime = System.currentTimeMillis();
+        System.out.println("程序运行的时间：" + (endTime - startTime) + "ms");
+    }
+}