HDFS-12176. dfsadmin shows DFS Used%: NaN% if the cluster has zero block. Contributed by Weiwei Yang.

(cherry picked from commit 770cc462281518545e3d1c0f8c21cf9ec9673200)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/DFSAdmin.java

@@ -519,9 +519,13 @@ public class DFSAdmin extends FsShell {
         + " (" + StringUtils.byteDesc(remaining) + ")");
     System.out.println("DFS Used: " + used
                        + " (" + StringUtils.byteDesc(used) + ")");
+    double dfsUsedPercent = 0;
+    if (presentCapacity != 0) {
+      dfsUsedPercent = used/(double)presentCapacity;
+    }
     System.out.println("DFS Used%: "
-        + StringUtils.formatPercent(used/(double)presentCapacity, 2));
-    
+        + StringUtils.formatPercent(dfsUsedPercent, 2));
+
     /* These counts are not always upto date. They are updated after  
      * iteration of an internal list. Should be updated in a few seconds to 
      * minutes. Use "-metaSave" to list of all such blocks and accurate