relpcace null check on token with isNotEmpty

Author: peterxcli

hadoop-ozone/integration-test/src/test/java/org/apache/hadoop/ozone/om/snapshot/TestOmSnapshot.java

@@ -18,7 +18,7 @@
 package org.apache.hadoop.ozone.om.snapshot;
 
 import static java.nio.charset.StandardCharsets.UTF_8;
-import static org.apache.commons.lang3.StringUtils.leftPad;
+import static org.apache.commons.lang3.StringUtils.isNotEmpty;
 import static org.apache.hadoop.hdds.HddsConfigKeys.HDDS_DB_PROFILE;
 import static org.apache.hadoop.ozone.OzoneAcl.AclScope.DEFAULT;
 import static org.apache.hadoop.ozone.OzoneConfigKeys.OZONE_SNAPSHOT_DELETING_SERVICE_INTERVAL;
@@ -2100,7 +2100,7 @@ public void testSnapshotDiffWhenOmRestartAndReportIsPartiallyFetched()
     await(POLL_MAX_WAIT_MILLIS, POLL_INTERVAL_MILLIS,
         () -> cluster.getOzoneManager().isRunning());
 
-    while (diffReport.getToken() != null) {
+    while (isNotEmpty(diffReport.getToken())) {
       diffReport = fetchReportPage(volumeName, bucketName, snapshot1,
           snapshot2, diffReport.getToken(), pageSize);
       diffReportEntries.addAll(diffReport.getDiffList());

hadoop-ozone/ozonefs-common/src/main/java/org/apache/hadoop/fs/ozone/BasicOzoneClientAdapterImpl.java

@@ -703,7 +703,7 @@ public SnapshotDiffReport getSnapshotDiffReport(Path snapshotDir,
       SnapshotDiffReportOzone report =
           getSnapshotDiffReportOnceComplete(fromSnapshot, toSnapshot, "");
       aggregated = report;
-      while (report.getToken() != null) {
+      while (StringUtils.isNotEmpty(report.getToken())) {
         LOG.info(
             "Total Snapshot Diff length between snapshot {} and {} exceeds"
                 + " max page size, Performing another " +

hadoop-ozone/ozonefs-common/src/main/java/org/apache/hadoop/fs/ozone/BasicRootedOzoneClientAdapterImpl.java

@@ -1367,7 +1367,7 @@ public SnapshotDiffReport getSnapshotDiffReport(Path snapshotDir,
           getSnapshotDiffReportOnceComplete(fromSnapshot, toSnapshot, volume,
               bucket, "");
       aggregated = report;
-      while (report.getToken() != null) {
+      while (StringUtils.isNotEmpty(report.getToken())) {
         LOG.info(
             "Total Snapshot Diff length between snapshot {} and {} exceeds"
                 + " max page size, Performing another" +