HDFS-16344. Improve DirectoryScanner.Stats#toString (#3695)

Reviewed-by: Viraj Jasani <vjasani@apache.org>
Reviewed-by: Ayush Saxena <ayushsaxena@apache.org>
Reviewed-by: Hui Fei <ferhui@apache.org>
(cherry picked from commit 829af89dc4)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DirectoryScanner.java

@@ -140,7 +140,8 @@ public String toString() {
           + ", missing metadata files: " + missingMetaFile
           + ", missing block files: " + missingBlockFile
           + ", missing blocks in memory: " + missingMemoryBlocks
-          + ", mismatched blocks: " + mismatchBlocks;
+          + ", mismatched blocks: " + mismatchBlocks
+          + ", duplicated blocks: " + duplicateBlocks;
     }
   }
 
@@ -355,7 +356,7 @@ private void clear() {
   }
 
   /**
-   * Main program loop for DirectoryScanner. Runs {@link reconcile()} and
+   * Main program loop for DirectoryScanner. Runs {@link #reconcile()} and
    * handles any exceptions.
    */
   @Override