diff --git a/docs/java.md b/docs/java.md
index 4a7cbe4c..8235b72b 100644
--- a/docs/java.md
+++ b/docs/java.md
@@ -782,6 +782,12 @@ try {
   System.out.println("always printed");
 }
 ```
+### util工具类
+```
+Collections
+Arrays
+Random
+```
 
 另见
 ---