diff --git a/docs/java/collection/java-collection-precautions-for-use.md b/docs/java/collection/java-collection-precautions-for-use.md
index cb68403f..9bd3a408 100644
--- a/docs/java/collection/java-collection-precautions-for-use.md
+++ b/docs/java/collection/java-collection-precautions-for-use.md
@@ -134,6 +134,7 @@ public static <T> T requireNonNull(T obj) {
     return obj;
 }
 ```
+> `Collectors`也提供了无需mergeFunction的`toMap()`方法，但此时若出现key冲突，则会抛出`duplicateKeyException`异常，因此强烈建议使用`toMap()`方法必填mergeFunction。
 
 ## 集合遍历