apache · adoroszlai · Mar 2, 2025 · Mar 1, 2025
diff --git a/dev-support/pmd/pmd-ruleset.xml b/dev-support/pmd/pmd-ruleset.xml
@@ -30,6 +30,7 @@
   <rule ref="category/java/bestpractices.xml/MissingOverride"/>
   <rule ref="category/java/bestpractices.xml/UnusedPrivateMethod"/>
   <rule ref="category/java/bestpractices.xml/UnusedPrivateField"/>
+  <rule ref="category/java/bestpractices.xml/UseCollectionIsEmpty" />
 
   <exclude-pattern>.*/generated-sources/.*</exclude-pattern>
 </ruleset>
diff --git a/hadoop-hdds/client/src/main/java/org/apache/hadoop/hdds/scm/storage/BlockInputStream.java b/hadoop-hdds/client/src/main/java/org/apache/hadoop/hdds/scm/storage/BlockInputStream.java
@@ -366,7 +366,7 @@ protected synchronized int readWithStrategy(ByteReaderStrategy strategy)
     int len = strategy.getTargetLength();
     while (len > 0) {
       // if we are at the last chunk and have read the entire chunk, return
-      if (chunkStreams.size() == 0 ||
+      if (chunkStreams.isEmpty() ||
           (chunkStreams.size() - 1 <= chunkIndex &&
               chunkStreams.get(chunkIndex)
                   .getRemaining() == 0)) {

diff --git a/hadoop-hdds/client/src/main/java/org/apache/hadoop/hdds/scm/storage/ECBlockOutputStream.java b/hadoop-hdds/client/src/main/java/org/apache/hadoop/hdds/scm/storage/ECBlockOutputStream.java
@@ -131,7 +131,7 @@ ContainerCommandResponseProto> executePutBlock(boolean close,
         blockID = bd.getBlockID();
       }
       List<ChunkInfo> chunks = bd.getChunks();
-      if (chunks != null && chunks.size() > 0) {
+      if (chunks != null && !chunks.isEmpty()) {
         if (chunks.get(0).hasStripeChecksum()) {
           checksumBlockData = bd;
           break;

diff --git a/...op-hdds/client/src/main/java/org/apache/hadoop/hdds/scm/storage/MultipartInputStream.java b/...op-hdds/client/src/main/java/org/apache/hadoop/hdds/scm/storage/MultipartInputStream.java
@@ -83,7 +83,7 @@ protected synchronized int readWithStrategy(ByteReaderStrategy strategy)
 
     int totalReadLen = 0;
     while (strategy.getTargetLength() > 0) {
-      if (partStreams.size() == 0 ||
+      if (partStreams.isEmpty() ||
           partStreams.size() - 1 <= partIndex &&
               partStreams.get(partIndex).getRemaining() == 0) {
         return totalReadLen == 0 ? EOF : totalReadLen;

diff --git a/hadoop-hdds/client/src/main/java/org/apache/hadoop/ozone/client/io/ECBlockInputStream.java b/hadoop-hdds/client/src/main/java/org/apache/hadoop/ozone/client/io/ECBlockInputStream.java
@@ -335,7 +335,7 @@ public synchronized int read(ByteBuffer byteBuffer) throws IOException {
 
   protected boolean shouldRetryFailedRead(int failedIndex) {
     Deque<DatanodeDetails> spareLocations = spareDataLocations.get(failedIndex);
-    if (spareLocations != null && spareLocations.size() > 0) {
+    if (spareLocations != null && !spareLocations.isEmpty()) {
       failedLocations.add(dataLocations[failedIndex]);
       DatanodeDetails spare = spareLocations.removeFirst();
       dataLocations[failedIndex] = spare;

diff --git a/hadoop-hdds/common/src/main/java/org/apache/hadoop/hdds/HddsUtils.java b/hadoop-hdds/common/src/main/java/org/apache/hadoop/hdds/HddsUtils.java
@@ -207,7 +207,7 @@ public static Optional<String> getHostName(String value) {
       return Optional.empty();
     }
     String hostname = value.replaceAll("\\:[0-9]+$", "");
-    if (hostname.length() == 0) {
+    if (hostname.isEmpty()) {
       return Optional.empty();
     } else {
       return Optional.of(hostname);

diff --git a/hadoop-hdds/common/src/main/java/org/apache/hadoop/hdds/scm/ha/SCMNodeInfo.java b/hadoop-hdds/common/src/main/java/org/apache/hadoop/hdds/scm/ha/SCMNodeInfo.java
@@ -79,7 +79,7 @@ public static List<SCMNodeInfo> buildNodeInfo(ConfigurationSource conf) {
     if (scmServiceId != null) {
       ArrayList< String > scmNodeIds = new ArrayList<>(
           HddsUtils.getSCMNodeIds(conf, scmServiceId));
-      if (scmNodeIds.size() == 0) {
+      if (scmNodeIds.isEmpty()) {
         throw new ConfigurationException(
             String.format("Configuration does not have any value set for %s " +
                     "for the SCM serviceId %s. List of SCM Node ID's should " +

diff --git a/hadoop-hdds/common/src/main/java/org/apache/hadoop/hdds/scm/net/InnerNodeImpl.java b/hadoop-hdds/common/src/main/java/org/apache/hadoop/hdds/scm/net/InnerNodeImpl.java
@@ -574,7 +574,7 @@ private Map<Node, Integer> getAncestorCountMap(Collection<Node> nodes,
     Preconditions.checkState(genToExclude >= 0);
     Preconditions.checkState(genToReturn >= 0);
 
-    if (nodes == null || nodes.size() == 0) {
+    if (nodes == null || nodes.isEmpty()) {
       return Collections.emptyMap();
     }
     // with the recursive call, genToReturn can be smaller than genToExclude
@@ -619,7 +619,7 @@ private Node getLeafOnLeafParent(int leafIndex, List<String> excludedScopes,
       if (excludedNodes != null && excludedNodes.contains(node)) {
         continue;
       }
-      if (excludedScopes != null && excludedScopes.size() > 0) {
+      if (excludedScopes != null && !excludedScopes.isEmpty()) {
         if (excludedScopes.stream().anyMatch(node::isDescendant)) {
           continue;
         }

diff --git a/...dds/common/src/main/java/org/apache/hadoop/hdds/security/ssl/ReloadingX509KeyManager.java b/...dds/common/src/main/java/org/apache/hadoop/hdds/security/ssl/ReloadingX509KeyManager.java
@@ -221,7 +221,7 @@ private X509ExtendedKeyManager init(PrivateKey newPrivateKey, List<X509Certifica
 
   private boolean isAlreadyUsing(PrivateKey privateKey, List<X509Certificate> newTrustChain) {
     return currentPrivateKey != null && currentPrivateKey.equals(privateKey) &&
-        currentTrustChain.size() > 0 &&
+        !currentTrustChain.isEmpty() &&
         newTrustChain.size() == currentTrustChain.size() &&
         newTrustChain.stream()
             .allMatch(

diff --git a/...s/common/src/main/java/org/apache/hadoop/hdds/security/ssl/ReloadingX509TrustManager.java b/...s/common/src/main/java/org/apache/hadoop/hdds/security/ssl/ReloadingX509TrustManager.java
@@ -161,7 +161,7 @@ private X509TrustManager init(List<X509Certificate> newRootCaCerts)
   }
 
   private boolean isAlreadyUsing(List<X509Certificate> newRootCaCerts) {
-    return newRootCaCerts.size() > 0 &&
+    return !newRootCaCerts.isEmpty() &&
         currentRootCACerts.size() == newRootCaCerts.size() &&
         newRootCaCerts.stream()
             .allMatch(

diff --git a/...in/java/org/apache/hadoop/hdds/security/x509/certificate/utils/SelfSignedCertificate.java b/...in/java/org/apache/hadoop/hdds/security/x509/certificate/utils/SelfSignedCertificate.java
@@ -144,7 +144,7 @@ private X509Certificate generateCertificate(BigInteger caCertSerialId) throws Op
       int keyUsageFlag = KeyUsage.keyCertSign | KeyUsage.cRLSign;
       KeyUsage keyUsage = new KeyUsage(keyUsageFlag);
       builder.addExtension(Extension.keyUsage, true, keyUsage);
-      if (altNames != null && altNames.size() >= 1) {
+      if (altNames != null && !altNames.isEmpty()) {
         builder.addExtension(new Extension(Extension.subjectAlternativeName,
             false, new GeneralNames(altNames.toArray(
                 new GeneralName[altNames.size()])).getEncoded()));

diff --git a/hadoop-hdds/common/src/main/java/org/apache/hadoop/hdds/tracing/StringCodec.java b/hadoop-hdds/common/src/main/java/org/apache/hadoop/hdds/tracing/StringCodec.java
@@ -50,7 +50,7 @@ public JaegerSpanContext extract(StringBuilder s) {
         throw new MalformedTracerStateStringException(value);
       } else {
         String traceId = parts[0];
-        if (traceId.length() <= 32 && traceId.length() >= 1) {
+        if (traceId.length() <= 32 && !traceId.isEmpty()) {
           return new JaegerSpanContext(high(traceId),
               (new BigInteger(traceId, 16)).longValue(),
               (new BigInteger(parts[1], 16)).longValue(),

diff --git a/hadoop-hdds/common/src/main/java/org/apache/hadoop/hdds/utils/BackgroundService.java b/hadoop-hdds/common/src/main/java/org/apache/hadoop/hdds/utils/BackgroundService.java
@@ -98,7 +98,7 @@ public int getThreadCount() {
   @VisibleForTesting
   public void runPeriodicalTaskNow() throws Exception {
     BackgroundTaskQueue tasks = getTasks();
-    while (tasks.size() > 0) {
+    while (!tasks.isEmpty()) {
       tasks.poll().call();
     }
   }
@@ -131,7 +131,7 @@ public synchronized void run() {
         LOG.debug("Number of background tasks to execute : {}", tasks.size());
       }
 
-      while (tasks.size() > 0) {
+      while (!tasks.isEmpty()) {
         BackgroundTask task = tasks.poll();
         CompletableFuture.runAsync(() -> {
           long startTime = System.nanoTime();

diff --git a/hadoop-hdds/common/src/main/java/org/apache/hadoop/ozone/common/ChecksumData.java b/hadoop-hdds/common/src/main/java/org/apache/hadoop/ozone/common/ChecksumData.java
@@ -116,12 +116,12 @@ public boolean verifyChecksumDataMatches(ChecksumData that, int startIndex)
       throws OzoneChecksumException {
 
     // pre checks
-    if (this.checksums.size() == 0) {
+    if (this.checksums.isEmpty()) {
       throw new OzoneChecksumException("Original checksumData has no " +
           "checksums");
     }
 
-    if (that.checksums.size() == 0) {
+    if (that.checksums.isEmpty()) {
       throw new OzoneChecksumException("Computed checksumData has no " +
           "checksums");
     }

diff --git a/hadoop-hdds/common/src/test/java/org/apache/hadoop/hdds/scm/net/TestNetworkTopologyImpl.java b/hadoop-hdds/common/src/test/java/org/apache/hadoop/hdds/scm/net/TestNetworkTopologyImpl.java
@@ -487,7 +487,7 @@ void testChooseRandomExcludedNode(NodeSchema[] schemas,
             excludedList, ancestorGen);
         for (Node key : dataNodes) {
           if (excludedList.contains(key) ||
-              (ancestorList.size() > 0 &&
+              (!ancestorList.isEmpty() &&
                   ancestorList.stream()
                       .map(a -> (InnerNode) a)
                       .anyMatch(a -> a.isAncestor(key)))) {
@@ -558,7 +558,7 @@ void testChooseRandomExcludedNodeAndScope(NodeSchema[] schemas,
                 excludedList, ancestorGen);
             for (Node key : dataNodes) {
               if (excludedList.contains(key) || key.isDescendant(path) ||
-                  (ancestorList.size() > 0 &&
+                  (!ancestorList.isEmpty() &&
                       ancestorList.stream()
                           .map(a -> (InnerNode) a)
                           .anyMatch(a -> a.isAncestor(key)))) {

diff --git a/hadoop-hdds/config/src/main/java/org/apache/hadoop/hdds/conf/StorageSize.java b/hadoop-hdds/config/src/main/java/org/apache/hadoop/hdds/conf/StorageSize.java
@@ -45,7 +45,7 @@ private static void checkState(boolean state, String errorString) {
   }
 
   public static StorageSize parse(String value) {
-    checkState(value != null && value.length() > 0, "value cannot be blank");
+    checkState(value != null && !value.isEmpty(), "value cannot be blank");
     String sanitizedValue = value.trim().toLowerCase(Locale.ENGLISH);
     StorageUnit parsedUnit = null;
     for (StorageUnit unit : StorageUnit.values()) {

diff --git a/...ice/src/main/java/org/apache/hadoop/ozone/container/common/statemachine/StateContext.java b/...ice/src/main/java/org/apache/hadoop/ozone/container/common/statemachine/StateContext.java
@@ -590,7 +590,7 @@ public boolean isThreadPoolAvailable(ExecutorService executor) {
     }
 
     ThreadPoolExecutor ex = (ThreadPoolExecutor) executor;
-    if (ex.getQueue().size() == 0) {
+    if (ex.getQueue().isEmpty()) {
       return true;
     }
 

diff --git a/...g/apache/hadoop/ozone/container/common/statemachine/commandhandler/CommandDispatcher.java b/...g/apache/hadoop/ozone/container/common/statemachine/commandhandler/CommandDispatcher.java
@@ -199,7 +199,7 @@ public CommandDispatcher build() {
           "Missing scm connection manager.");
       Preconditions.checkNotNull(this.container, "Missing ozone container.");
       Preconditions.checkNotNull(this.context, "Missing state context.");
-      Preconditions.checkArgument(this.handlerList.size() > 0,
+      Preconditions.checkArgument(!this.handlerList.isEmpty(),
           "The number of command handlers must be greater than 0.");
       return new CommandDispatcher(this.container, this.connectionManager,
           this.context, handlerList.toArray(

diff --git a/...in/java/org/apache/hadoop/ozone/container/common/states/endpoint/VersionEndpointTask.java b/...in/java/org/apache/hadoop/ozone/container/common/states/endpoint/VersionEndpointTask.java
@@ -132,7 +132,7 @@ private void checkVolumeSet(MutableVolumeSet volumeSet,
           volumeSet.failVolume(volume.getStorageDir().getPath());
         }
       }
-      if (volumeSet.getVolumesList().size() == 0) {
+      if (volumeSet.getVolumesList().isEmpty()) {
         // All volumes are in inconsistent state
         throw new DiskOutOfSpaceException(
             "All configured Volumes are in Inconsistent State");

diff --git a/...rvice/src/main/java/org/apache/hadoop/ozone/container/common/volume/MutableVolumeSet.java b/...rvice/src/main/java/org/apache/hadoop/ozone/container/common/volume/MutableVolumeSet.java
@@ -189,7 +189,7 @@ private void initializeVolumeSet() throws IOException {
 
     // First checking if we have any volumes, if all volumes are failed the
     // volumeMap size will be zero, and we throw Exception.
-    if (volumeMap.size() == 0) {
+    if (volumeMap.isEmpty()) {
       throw new DiskOutOfSpaceException("No storage locations configured");
     }
   }
@@ -219,7 +219,7 @@ public void checkAllVolumes(StorageVolumeChecker checker)
       throw new IOException("Interrupted while running disk check", e);
     }
 
-    if (failedVolumes.size() > 0) {
+    if (!failedVolumes.isEmpty()) {
       LOG.warn("checkAllVolumes got {} failed volumes - {}",
           failedVolumes.size(), failedVolumes);
       handleVolumeFailures(failedVolumes);
@@ -266,7 +266,7 @@ public void checkVolumeAsync(StorageVolume volume) {
 
     volumeChecker.checkVolume(
         volume, (healthyVolumes, failedVolumes) -> {
-          if (failedVolumes.size() > 0) {
+          if (!failedVolumes.isEmpty()) {
             LOG.warn("checkVolumeAsync callback got {} failed volumes: {}",
                 failedVolumes.size(), failedVolumes);
           } else {
@@ -441,7 +441,7 @@ public boolean hasEnoughVolumes() {
     boolean hasEnoughVolumes;
     if (maxVolumeFailuresTolerated ==
         StorageVolumeChecker.MAX_VOLUME_FAILURE_TOLERATED_LIMIT) {
-      hasEnoughVolumes = getVolumesList().size() >= 1;
+      hasEnoughVolumes = !getVolumesList().isEmpty();
     } else {
       hasEnoughVolumes = getFailedVolumesList().size() <= maxVolumeFailuresTolerated;
     }

diff --git a/.../java/org/apache/hadoop/ozone/container/common/volume/RoundRobinVolumeChoosingPolicy.java b/.../java/org/apache/hadoop/ozone/container/common/volume/RoundRobinVolumeChoosingPolicy.java
@@ -45,7 +45,7 @@ public HddsVolume chooseVolume(List<HddsVolume> volumes,
       long maxContainerSize) throws IOException {
 
     // No volumes available to choose from
-    if (volumes.size() < 1) {
+    if (volumes.isEmpty()) {
       throw new DiskOutOfSpaceException("No more available volumes");
     }
 

diff --git a/...java/org/apache/hadoop/ozone/container/ec/reconstruction/ECReconstructionCoordinator.java b/...java/org/apache/hadoop/ozone/container/ec/reconstruction/ECReconstructionCoordinator.java
@@ -289,7 +289,7 @@ public void reconstructECBlockGroup(BlockLocationInfo blockLocationInfo,
           emptyBlockStreams[i] = getECBlockOutputStream(blockLocationInfo, datanodeDetails, repConfig, replicaIndex);
         }
 
-        if (toReconstructIndexes.size() > 0) {
+        if (!toReconstructIndexes.isEmpty()) {
           sis.setRecoveryIndexes(toReconstructIndexes.stream().map(i -> (i - 1))
               .collect(Collectors.toSet()));
           long length = safeBlockGroupLength;

diff --git a/...r-service/src/main/java/org/apache/hadoop/ozone/container/keyvalue/KeyValueContainer.java b/...r-service/src/main/java/org/apache/hadoop/ozone/container/keyvalue/KeyValueContainer.java
@@ -229,7 +229,7 @@ public void create(VolumeSet volumeSet, VolumeChoosingPolicy
           LOG.error("Exception attempting to create container {} on volume {}" +
               " remaining volumes to try {}", containerData.getContainerID(),
               containerVolume.getHddsRootDir(), volumes.size(), ex);
-          if (volumes.size() == 0) {
+          if (volumes.isEmpty()) {
             throw new StorageContainerException(
                 "Container creation failed. " + ex.getMessage(), ex,
                 CONTAINER_INTERNAL_ERROR);

diff --git a/...vice/src/main/java/org/apache/hadoop/ozone/container/keyvalue/KeyValueContainerCheck.java b/...vice/src/main/java/org/apache/hadoop/ozone/container/keyvalue/KeyValueContainerCheck.java
@@ -354,7 +354,7 @@ private ScanResult scanBlock(BlockData block, DataTransferThrottler throttler,
         // In EC, client may write empty putBlock in padding block nodes.
         // So, we need to make sure, chunk length > 0, before declaring
         // the missing chunk file.
-        if (block.getChunks().size() > 0 && block
+        if (!block.getChunks().isEmpty() && block
             .getChunks().get(0).getLen() > 0) {
           return ScanResult.unhealthy(ScanResult.FailureType.MISSING_CHUNK_FILE,
               chunkFile, new IOException("Missing chunk file " +

diff --git a/...ava/org/apache/hadoop/hdds/security/x509/certificate/client/DefaultCertificateClient.java b/...ava/org/apache/hadoop/hdds/security/x509/certificate/client/DefaultCertificateClient.java
@@ -428,7 +428,7 @@ public synchronized List<X509Certificate> getTrustChain()
       if (cert != null) {
         chain.add(cert);
       }
-      Preconditions.checkState(chain.size() > 0, "Empty trust chain");
+      Preconditions.checkState(!chain.isEmpty(), "Empty trust chain");
     }
     return chain;
   }

diff --git a/hadoop-hdds/framework/src/main/java/org/apache/hadoop/hdds/utils/db/DBConfigFromFile.java b/hadoop-hdds/framework/src/main/java/org/apache/hadoop/hdds/utils/db/DBConfigFromFile.java
@@ -115,7 +115,7 @@ public static ManagedDBOptions readFromFile(String dbFileName,
       List<ColumnFamilyDescriptor> cfDescs) throws IOException {
     Preconditions.checkNotNull(dbFileName);
     Preconditions.checkNotNull(cfDescs);
-    Preconditions.checkArgument(cfDescs.size() > 0);
+    Preconditions.checkArgument(!cfDescs.isEmpty());
 
     //TODO: Add Documentation on how to support RocksDB Mem Env.
     Env env = Env.getDefault();

diff --git a/hadoop-hdds/framework/src/main/java/org/apache/hadoop/hdds/utils/db/DBStoreBuilder.java b/hadoop-hdds/framework/src/main/java/org/apache/hadoop/hdds/utils/db/DBStoreBuilder.java
@@ -444,7 +444,7 @@ private ManagedDBOptions getDBOptionsFromFile(
         columnFamilyDescriptors.add(tc.getDescriptor());
       }
 
-      if (columnFamilyDescriptors.size() > 0) {
+      if (!columnFamilyDescriptors.isEmpty()) {
         try {
           option = DBConfigFromFile.readFromFile(dbname,
               columnFamilyDescriptors);

diff --git a/hadoop-hdds/framework/src/main/java/org/apache/hadoop/hdds/utils/db/RDBStore.java b/hadoop-hdds/framework/src/main/java/org/apache/hadoop/hdds/utils/db/RDBStore.java
@@ -443,7 +443,7 @@ public DBUpdatesWrapper getUpdatesSince(long sequenceNumber, long limitCount)
           sequenceNumber, e);
       dbUpdatesWrapper.setDBUpdateSuccess(false);
     } finally {
-      if (dbUpdatesWrapper.getData().size() > 0) {
+      if (!dbUpdatesWrapper.getData().isEmpty()) {
         rdbMetrics.incWalUpdateDataSize(cumulativeDBUpdateLogBatchSize);
         rdbMetrics.incWalUpdateSequenceCount(
             dbUpdatesWrapper.getCurrentSequenceNumber() - sequenceNumber);

diff --git a/hadoop-hdds/framework/src/main/java/org/apache/hadoop/hdds/utils/db/RDBTable.java b/hadoop-hdds/framework/src/main/java/org/apache/hadoop/hdds/utils/db/RDBTable.java
@@ -332,7 +332,7 @@ && get(startKey) == null) {
                           currentKey, null))) {
             result.add(currentEntry);
           } else {
-            if (result.size() > 0 && sequential) {
+            if (!result.isEmpty() && sequential) {
               // if the caller asks for a sequential range of results,
               // and we met a dis-match, abort iteration from here.
               // if result is empty, we continue to look for the first match.

diff --git a/...p-hdds/framework/src/main/java/org/apache/hadoop/ozone/upgrade/BasicUpgradeFinalizer.java b/...p-hdds/framework/src/main/java/org/apache/hadoop/ozone/upgrade/BasicUpgradeFinalizer.java
@@ -124,7 +124,7 @@ public synchronized StatusAndMessages reportStatus(
     assertClientId(upgradeClientID);
     List<String> returningMsgs = new ArrayList<>(msgs.size() + 10);
     Status status = versionManager.getUpgradeState();
-    while (msgs.size() > 0) {
+    while (!msgs.isEmpty()) {
       returningMsgs.add(msgs.poll());
     }
     return new StatusAndMessages(status, returningMsgs);

diff --git a/hadoop-hdds/rocks-native/src/test/java/org/apache/hadoop/hdds/utils/TestUtils.java b/hadoop-hdds/rocks-native/src/test/java/org/apache/hadoop/hdds/utils/TestUtils.java
@@ -48,7 +48,7 @@ public static String getLexicographicallyHigherString(String val) {
   public static List<Optional<String>> getTestingBounds(
       SortedMap<String, Integer> keys) {
     Set<String> boundary = new HashSet<>();
-    if (keys.size() > 0) {
+    if (!keys.isEmpty()) {
       List<String> sortedKeys = new ArrayList<>(keys.keySet());
       boundary.add(getLexicographicallyLowerString(keys.firstKey()));
       boundary.add(keys.firstKey());

diff --git a/...eckpoint-differ/src/test/java/org/apache/ozone/rocksdiff/TestRocksDBCheckpointDiffer.java b/...eckpoint-differ/src/test/java/org/apache/ozone/rocksdiff/TestRocksDBCheckpointDiffer.java
@@ -925,7 +925,7 @@ private void traverseGraph(
       // fist go through fwdGraph to find nodes that don't have successors.
       // These nodes will be the top level nodes in reverse graph
       Set<CompactionNode> successors = fwdMutableGraph.successors(infileNode);
-      if (successors.size() == 0) {
+      if (successors.isEmpty()) {
         LOG.debug("No successors. Cumulative keys: {}, total keys: {}",
             infileNode.getCumulativeKeysReverseTraversal(),
             infileNode.getTotalNumberOfKeys());

diff --git a/...op-hdds/server-scm/src/main/java/org/apache/hadoop/hdds/scm/SCMCommonPlacementPolicy.java b/...op-hdds/server-scm/src/main/java/org/apache/hadoop/hdds/scm/SCMCommonPlacementPolicy.java
@@ -235,7 +235,7 @@ protected List<DatanodeDetails> chooseDatanodesInternal(
       healthyNodes.removeAll(usedNodes);
     }
     String msg;
-    if (healthyNodes.size() == 0) {
+    if (healthyNodes.isEmpty()) {
       msg = "No healthy node found to allocate container.";
       LOG.error(msg);
       throw new SCMException(msg, SCMException.ResultCodes
@@ -440,7 +440,7 @@ public ContainerPlacementStatus validateContainerPlacement(
     // We have a network topology so calculate if it is satisfied or not.
     int requiredRacks = getRequiredRackCount(replicas, 0);
     if (topology == null || replicas == 1 || requiredRacks == 1) {
-      if (dns.size() > 0) {
+      if (!dns.isEmpty()) {
         // placement is always satisfied if there is at least one DN.
         return validPlacement;
       } else {
@@ -556,7 +556,7 @@ public Set<ContainerReplica> replicasToCopyToFixMisreplication(
                 .limit(numberOfReplicasToBeCopied)
                 .collect(Collectors.toList());
         if (numberOfReplicasToBeCopied > replicasToBeCopied.size()) {
-          Node rack = replicaList.size() > 0 ? this.getPlacementGroup(
+          Node rack = !replicaList.isEmpty() ? this.getPlacementGroup(
                   replicaList.get(0).getDatanodeDetails()) : null;
           LOG.warn("Not enough copyable replicas available in rack {}. " +
                   "Required number of Replicas to be copied: {}." +
@@ -641,14 +641,14 @@ public Set<ContainerReplica> replicasToRemoveToFixOverreplication(
         Node rack = pq.poll();
         Set<ContainerReplica> replicaSet =
                 placementGroupReplicaIdMap.get(rack).get(rid);
-        if (replicaSet.size() > 0) {
+        if (!replicaSet.isEmpty()) {
           ContainerReplica r = replicaSet.stream().findFirst().get();
           replicasToRemove.add(r);
           replicaSet.remove(r);
           replicaIdMap.get(rid).remove(r);
           placementGroupCntMap.compute(rack,
                   (group, cnt) -> (cnt == null ? 0 : cnt) - 1);
-          if (replicaSet.size() == 0) {
+          if (replicaSet.isEmpty()) {
             placementGroupReplicaIdMap.get(rack).remove(rid);
           } else {
             pq.add(rack);

diff --git a/...apache/hadoop/hdds/scm/container/placement/algorithms/SCMContainerPlacementRackAware.java b/...apache/hadoop/hdds/scm/container/placement/algorithms/SCMContainerPlacementRackAware.java
@@ -146,7 +146,7 @@ protected List<DatanodeDetails> chooseDatanodesInternal(
     }
     DatanodeDetails favoredNode;
     int favorIndex = 0;
-    if (mutableUsedNodes.size() == 0) {
+    if (mutableUsedNodes.isEmpty()) {
       // choose all nodes for a new pipeline case
       // choose first datanode from scope ROOT or from favoredNodes if not null
       favoredNode = favoredNodeNum > favorIndex ?