diff --git a/88. 保护性的编写 readObject 方法.md b/88. 保护性的编写 readObject 方法.md
index 3a03604..adccdf7 100644
--- a/88. 保护性的编写 readObject 方法.md	
+++ b/88. 保护性的编写 readObject 方法.md	
@@ -17,8 +17,7 @@ public final class Period {
         this.start = new Date(start.getTime());
         this.end = new Date(end.getTime());
         if (this.start.compareTo(this.end) > 0)
-        throw new IllegalArgumentException(
-        start + " after " + end);
+            throw new IllegalArgumentException(start + " after " + end);
     }
     public Date start () {
         return new Date(start.getTime());