diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DatanodeUtil.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DatanodeUtil.java
index ab3d8ab96cacb..07edaa12125de 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DatanodeUtil.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DatanodeUtil.java
@@ -132,10 +132,11 @@ public static File idToBlockDir(File root, long blockId) {
   }
 
   /**
-   * Take an example: we hava a block with blockid mapping to:
+   * Take an example.
+   * We hava a block with blockid mapping to:
    * "/data1/hadoop/hdfs/datanode/current/BP-xxxx/current/finalized/subdir0/subdir0"
-   * We return "subdir0/subdir0"
-   * @return
+   * We return "subdir0/subdir0".
+   * @return two-level subdir string where block will be stored.
    */
   public static String idToBlockDirSuffixName(long blockId) {
     int d1 = (int) ((blockId >> 16) & 0x1F);