diff --git a/codes/java/chapter_hashing/array_hash_map.java b/codes/java/chapter_hashing/array_hash_map.java
index 89082c2f9..6dc26ba16 100644
--- a/codes/java/chapter_hashing/array_hash_map.java
+++ b/codes/java/chapter_hashing/array_hash_map.java
@@ -52,7 +52,7 @@ class ArrayHashMap {
     /* 删除操作 */
     public void remove(int key) {
         int index = hashFunc(key);
-        // 置为空字符，代表删除
+        // 置为 null ，代表删除
         bucket.set(index, null);
     }
 
diff --git a/docs/chapter_hashing/hash_map.md b/docs/chapter_hashing/hash_map.md
index 793d90323..4dd325a2e 100644
--- a/docs/chapter_hashing/hash_map.md
+++ b/docs/chapter_hashing/hash_map.md
@@ -233,7 +233,7 @@ $$
         /* 删除操作 */
         public void remove(int key) {
             int index = hashFunc(key);
-            // 置为空字符，代表删除
+            // 置为 null，代表删除
             bucket.set(index, null);
         }
     }