[IOTDB-5284] Fix some iotdb-server code smells (#8738)

* fix some code smells

server/src/main/java/org/apache/iotdb/db/auth/ClusterAuthorityFetcher.java

@@ -258,9 +258,9 @@ public class ClusterAuthorityFetcher implements IAuthorityFetcher {
     List<PathPrivilege> pathPrivilegeList = new ArrayList<>();
     user.setName(tPermissionInfoResp.getUserInfo().getUsername());
     user.setPassword(tPermissionInfoResp.getUserInfo().getPassword());
-    for (int i = 0; i < privilegeList.size(); i++) {
+    for (int i = 0; i < privilegeList.size(); i += 2) {
       String path = privilegeList.get(i);
-      String privilege = privilegeList.get(++i);
+      String privilege = privilegeList.get(i + 1);
       pathPrivilegeList.add(toPathPrivilege(path, privilege));
     }
     user.setOpenIdUser(tPermissionInfoResp.getUserInfo().isIsOpenIdUser());
@@ -278,9 +278,9 @@ public class ClusterAuthorityFetcher implements IAuthorityFetcher {
     List<String> privilegeList = tPermissionInfoResp.getRoleInfo().get(roleName).getPrivilegeList();
     List<PathPrivilege> pathPrivilegeList = new ArrayList<>();
     role.setName(tPermissionInfoResp.getRoleInfo().get(roleName).getRoleName());
-    for (int i = 0; i < privilegeList.size(); i++) {
+    for (int i = 0; i < privilegeList.size(); i += 2) {
       String path = privilegeList.get(i);
-      String privilege = privilegeList.get(++i);
+      String privilege = privilegeList.get(i + 1);
       pathPrivilegeList.add(toPathPrivilege(path, privilege));
     }
     role.setPrivilegeList(pathPrivilegeList);

server/src/main/java/org/apache/iotdb/db/client/ConfigNodeClient.java

@@ -148,7 +148,7 @@ public class ConfigNodeClient
   public static final String MSG_RECONNECTION_FAIL =
       "Fail to connect to any config node. Please check status of ConfigNodes";
 
-  private static final int retryIntervalMs = 1000;
+  private static final int RETRY_INTERVAL_MS = 1000;
 
   private long connectionTimeout = ClientPoolProperty.DefaultProperty.WAIT_CLIENT_TIMEOUT_MS;
 
@@ -226,7 +226,7 @@ public class ConfigNodeClient
   private void waitAndReconnect() throws TException {
     try {
       // wait to start the next try
-      Thread.sleep(retryIntervalMs);
+      Thread.sleep(RETRY_INTERVAL_MS);
     } catch (InterruptedException e) {
       Thread.currentThread().interrupt();
       throw new TException(

server/src/main/java/org/apache/iotdb/db/client/ConfigNodeInfo.java

@@ -44,7 +44,7 @@ public class ConfigNodeInfo {
 
   private static final Logger logger = LoggerFactory.getLogger(ConfigNodeInfo.class);
 
-  private final String CONFIG_NODE_LIST = "config_node_list";
+  private static final String CONFIG_NODE_LIST = "config_node_list";
 
   private static final String PROPERTIES_FILE_NAME = "system.properties";
 

server/src/main/java/org/apache/iotdb/db/conf/IoTDBConfig.java

@@ -193,10 +193,10 @@ public class IoTDBConfig {
   private int walBufferQueueCapacity = 50;
 
   /** Size threshold of each wal file. Unit: byte */
-  private volatile long walFileSizeThresholdInByte = 10 * 1024 * 1024;
+  private volatile long walFileSizeThresholdInByte = 10 * 1024 * 1024L;
 
   /** Size threshold of each checkpoint file. Unit: byte */
-  private volatile long checkpointFileSizeThresholdInByte = 3 * 1024 * 1024;
+  private volatile long checkpointFileSizeThresholdInByte = 3 * 1024 * 1024L;
 
   /** Minimum ratio of effective information in wal files */
   private volatile double walMinEffectiveInfoRatio = 0.1;
@@ -206,13 +206,13 @@ public class IoTDBConfig {
    * this, wal can flush this memtable to disk, otherwise wal will snapshot this memtable in wal.
    * Unit: byte
    */
-  private volatile long walMemTableSnapshotThreshold = 8 * 1024 * 1024;
+  private volatile long walMemTableSnapshotThreshold = 8 * 1024 * 1024L;
 
   /** MemTable's max snapshot number in wal file */
   private volatile int maxWalMemTableSnapshotNum = 1;
 
   /** The period when outdated wal files are periodically deleted. Unit: millisecond */
-  private volatile long deleteWalFilesPeriodInMs = 20 * 1000;
+  private volatile long deleteWalFilesPeriodInMs = 20 * 1000L;
   // endregion
 
   /**
@@ -1001,7 +1001,7 @@ public class IoTDBConfig {
   private long throttleThreshold = 50 * 1024 * 1024 * 1024L;
 
   /** Maximum wait time of write cache in IoTConsensus. Unit: ms */
-  private long cacheWindowTimeInMs = 10 * 1000;
+  private long cacheWindowTimeInMs = 10 * 1000L;
 
   private long dataRatisConsensusLogAppenderBufferSizeMax = 4 * 1024 * 1024L;
   private long schemaRatisConsensusLogAppenderBufferSizeMax = 4 * 1024 * 1024L;
@@ -1297,8 +1297,8 @@ public class IoTDBConfig {
         || "us".equals(timestampPrecision)
         || "ns".equals(timestampPrecision))) {
       logger.error(
-          "Wrong timestamp precision, please set as: ms, us or ns ! Current is: "
-              + timestampPrecision);
+          "Wrong timestamp precision, please set as: ms, us or ns ! Current is: {}",
+          timestampPrecision);
       System.exit(-1);
     }
     this.timestampPrecision = timestampPrecision;

server/src/main/java/org/apache/iotdb/db/conf/IoTDBStartCheck.java

@@ -162,7 +162,7 @@ public class IoTDBStartCheck {
   }
 
   private IoTDBStartCheck() {
-    logger.info("Starting IoTDB " + IoTDBConstant.VERSION_WITH_BUILD);
+    logger.info("Starting IoTDB {}", IoTDBConstant.VERSION_WITH_BUILD);
 
     // check whether SCHEMA_DIR exists, create if not exists
     File dir = SystemFileFactory.INSTANCE.getFile(SCHEMA_DIR);

server/src/main/java/org/apache/iotdb/db/engine/cache/BloomFilterCache.java

@@ -53,7 +53,7 @@ public class BloomFilterCache {
 
   private BloomFilterCache() {
     if (CACHE_ENABLE) {
-      logger.info("BloomFilterCache size = " + MEMORY_THRESHOLD_IN_BLOOM_FILTER_CACHE);
+      logger.info("BloomFilterCache size = {}", MEMORY_THRESHOLD_IN_BLOOM_FILTER_CACHE);
     }
     lruCache =
         Caffeine.newBuilder()
@@ -99,7 +99,7 @@ public class BloomFilterCache {
     BloomFilter bloomFilter = lruCache.get(key);
 
     if (debug) {
-      DEBUG_LOGGER.info("get bloomFilter from cache where filePath is: " + key.filePath);
+      DEBUG_LOGGER.info("get bloomFilter from cache where filePath is: {}", key.filePath);
     }
 
     return bloomFilter;

server/src/main/java/org/apache/iotdb/db/engine/cache/ChunkCache.java

@@ -64,7 +64,7 @@ public class ChunkCache {
 
   private ChunkCache() {
     if (CACHE_ENABLE) {
-      logger.info("ChunkCache size = " + MEMORY_THRESHOLD_IN_CHUNK_CACHE);
+      logger.info("ChunkCache size = {}", MEMORY_THRESHOLD_IN_CHUNK_CACHE);
     }
     lruCache =
         Caffeine.newBuilder()
@@ -127,7 +127,7 @@ public class ChunkCache {
       Chunk chunk = lruCache.get(chunkMetaData);
 
       if (debug) {
-        DEBUG_LOGGER.info("get chunk from cache whose meta data is: " + chunkMetaData);
+        DEBUG_LOGGER.info("get chunk from cache whose meta data is: {}", chunkMetaData);
       }
 
       return new Chunk(

server/src/main/java/org/apache/iotdb/db/engine/cache/TimeSeriesMetadataCache.java

@@ -84,7 +84,7 @@ public class TimeSeriesMetadataCache {
   private TimeSeriesMetadataCache() {
     if (CACHE_ENABLE) {
       logger.info(
-          "TimeseriesMetadataCache size = " + MEMORY_THRESHOLD_IN_TIME_SERIES_METADATA_CACHE);
+          "TimeseriesMetadataCache size = {}", MEMORY_THRESHOLD_IN_TIME_SERIES_METADATA_CACHE);
     }
     lruCache =
         Caffeine.newBuilder()

server/src/main/java/org/apache/iotdb/db/engine/compaction/execute/exception/CompactionExceptionHandler.java

@@ -121,7 +121,7 @@ public class CompactionExceptionHandler {
         lostFiles.add(tsFileResource);
       }
     }
-    return lostFiles.size() == 0;
+    return lostFiles.isEmpty();
   }
 
   /**

server/src/main/java/org/apache/iotdb/db/engine/compaction/execute/performer/ICrossCompactionPerformer.java

@@ -23,5 +23,6 @@ import org.apache.iotdb.db.engine.storagegroup.TsFileResource;
 import java.util.List;
 
 public interface ICrossCompactionPerformer extends ICompactionPerformer {
+  @Override
   void setSourceFiles(List<TsFileResource> seqFiles, List<TsFileResource> unseqFiles);
 }

server/src/main/java/org/apache/iotdb/db/engine/compaction/execute/performer/ISeqCompactionPerformer.java

@@ -23,5 +23,6 @@ import org.apache.iotdb.db.engine.storagegroup.TsFileResource;
 import java.util.List;
 
 public interface ISeqCompactionPerformer extends ICompactionPerformer {
+  @Override
   void setSourceFiles(List<TsFileResource> seqFiles);
 }

server/src/main/java/org/apache/iotdb/db/engine/compaction/execute/performer/IUnseqCompactionPerformer.java

@@ -23,5 +23,6 @@ import org.apache.iotdb.db.engine.storagegroup.TsFileResource;
 import java.util.List;
 
 public interface IUnseqCompactionPerformer extends ICompactionPerformer {
+  @Override
   void setSourceFiles(List<TsFileResource> unseqFiles);
 }

server/src/main/java/org/apache/iotdb/db/engine/compaction/execute/performer/impl/FastCompactionPerformer.java

@@ -110,7 +110,7 @@ public class FastCompactionPerformer
   public void perform()
       throws IOException, MetadataException, StorageEngineException, InterruptedException {
     TsFileMetricManager.getInstance()
-        .addCompactionTempFileNum(!isCrossCompaction, seqFiles.size() > 0, targetFiles.size());
+        .addCompactionTempFileNum(!isCrossCompaction, !seqFiles.isEmpty(), targetFiles.size());
     try (MultiTsFileDeviceIterator deviceIterator =
             new MultiTsFileDeviceIterator(seqFiles, unseqFiles, readerCacheMap);
         AbstractCompactionWriter compactionWriter =
@@ -146,7 +146,7 @@ public class FastCompactionPerformer
         long currentTempFileSize = compactionWriter.getWriterSize();
         TsFileMetricManager.getInstance()
             .addCompactionTempFileSize(
-                !isCrossCompaction, seqFiles.size() > 0, currentTempFileSize - tempFileSize);
+                !isCrossCompaction, !seqFiles.isEmpty(), currentTempFileSize - tempFileSize);
         tempFileSize = currentTempFileSize;
         sortedSourceFiles.clear();
       }
@@ -161,9 +161,9 @@ public class FastCompactionPerformer
       readerCacheMap = null;
       modificationCache = null;
       TsFileMetricManager.getInstance()
-          .addCompactionTempFileNum(!isCrossCompaction, seqFiles.size() > 0, -targetFiles.size());
+          .addCompactionTempFileNum(!isCrossCompaction, !seqFiles.isEmpty(), -targetFiles.size());
       TsFileMetricManager.getInstance()
-          .addCompactionTempFileSize(!isCrossCompaction, seqFiles.size() > 0, -tempFileSize);
+          .addCompactionTempFileSize(!isCrossCompaction, !seqFiles.isEmpty(), -tempFileSize);
     }
   }
 

server/src/main/java/org/apache/iotdb/db/engine/compaction/execute/performer/impl/ReadChunkCompactionPerformer.java

@@ -69,7 +69,7 @@ public class ReadChunkCompactionPerformer implements ISeqCompactionPerformer {
     // size for file writer is 5% of per compaction task memory budget
     long sizeForFileWriter =
         (long)
-            (SystemInfo.getInstance().getMemorySizeForCompaction()
+            ((double) SystemInfo.getInstance().getMemorySizeForCompaction()
                 / IoTDBDescriptor.getInstance().getConfig().getCompactionThreadCount()
                 * IoTDBDescriptor.getInstance().getConfig().getChunkMetadataSizeProportion());
     TsFileMetricManager.getInstance().addCompactionTempFileNum(true, true, 1);

server/src/main/java/org/apache/iotdb/db/engine/compaction/execute/performer/impl/ReadPointCompactionPerformer.java

@@ -104,7 +104,7 @@ public class ReadPointCompactionPerformer
         .getQueryFileManager()
         .addUsedFilesForQuery(queryId, queryDataSource);
     TsFileMetricManager.getInstance()
-        .addCompactionTempFileNum(seqFiles.size() == 0, false, targetFiles.size());
+        .addCompactionTempFileNum(seqFiles.isEmpty(), false, targetFiles.size());
     try (AbstractCompactionWriter compactionWriter =
         getCompactionWriter(seqFiles, unseqFiles, targetFiles)) {
       // Do not close device iterator, because tsfile reader is managed by FileReaderManager.
@@ -132,9 +132,9 @@ public class ReadPointCompactionPerformer
     } finally {
       QueryResourceManager.getInstance().endQuery(queryId);
       TsFileMetricManager.getInstance()
-          .addCompactionTempFileNum(seqFiles.size() == 0, false, -targetFiles.size());
+          .addCompactionTempFileNum(seqFiles.isEmpty(), false, -targetFiles.size());
       TsFileMetricManager.getInstance()
-          .addCompactionTempFileSize(seqFiles.size() == 0, false, tempFileSize);
+          .addCompactionTempFileSize(seqFiles.isEmpty(), false, tempFileSize);
     }
   }
 
@@ -187,7 +187,7 @@ public class ReadPointCompactionPerformer
     // add temp file metrics
     long currentWriterSize = compactionWriter.getWriterSize();
     TsFileMetricManager.getInstance()
-        .addCompactionTempFileSize(seqFiles.size() == 0, false, currentWriterSize - tempFileSize);
+        .addCompactionTempFileSize(seqFiles.isEmpty(), false, currentWriterSize - tempFileSize);
     tempFileSize = currentWriterSize;
   }
 
@@ -240,7 +240,7 @@ public class ReadPointCompactionPerformer
     // add temp file metrics
     long currentWriterSize = compactionWriter.getWriterSize();
     TsFileMetricManager.getInstance()
-        .addCompactionTempFileSize(seqFiles.size() == 0, false, currentWriterSize - tempFileSize);
+        .addCompactionTempFileSize(seqFiles.isEmpty(), false, currentWriterSize - tempFileSize);
     tempFileSize = currentWriterSize;
   }
 

server/src/main/java/org/apache/iotdb/db/engine/compaction/execute/recover/CompactionRecoverTask.java

@@ -365,10 +365,7 @@ public class CompactionRecoverTask {
               tsFileManager.getStorageGroupDir()
                   + File.separator
                   + IoTDBConstant.COMPACTION_MODIFICATION_FILE_NAME_FROM_OLD);
-      if (!checkAndDeleteFile(compactionModsFileFromOld)) {
-        return false;
-      }
-      return true;
+      return checkAndDeleteFile(compactionModsFileFromOld);
     }
 
     /**

server/src/main/java/org/apache/iotdb/db/engine/compaction/execute/task/InnerSpaceCompactionTask.java

@@ -256,7 +256,7 @@ public class InnerSpaceCompactionTask extends AbstractCompactionTask {
           dataRegionId,
           targetTsFileResource.getTsFile().getName(),
           costTime,
-          ((double) selectedFileSize) / 1024.0d / 1024.0d / costTime);
+          selectedFileSize / 1024.0d / 1024.0d / costTime);
 
       if (logFile.exists()) {
         FileUtils.delete(logFile);

server/src/main/java/org/apache/iotdb/db/engine/compaction/execute/utils/MultiTsFileDeviceIterator.java

@@ -305,7 +305,7 @@ public class MultiTsFileDeviceIterator implements AutoCloseable {
       TsFileSequenceReader reader = readerMap.get(tsFileResource);
       List<AlignedChunkMetadata> alignedChunkMetadataList =
           reader.getAlignedChunkMetadata(currentDevice.left);
-      if (alignedChunkMetadataList.size() > 0) {
+      if (!alignedChunkMetadataList.isEmpty()) {
         alignedChunkMetadataList.forEach(x -> x.setFilePath(tsFileResource.getTsFilePath()));
       }
       applyModificationForAlignedChunkMetadataList(tsFileResource, alignedChunkMetadataList);
@@ -429,7 +429,7 @@ public class MultiTsFileDeviceIterator implements AutoCloseable {
         }
         tempCollectedSeries.addAll(chunkMetadataListMap.keySet());
       }
-      if (tempCollectedSeries.size() > 0) {
+      if (!tempCollectedSeries.isEmpty()) {
         if (!hasRemainingSeries()) {
           lastSeries = Collections.max(tempCollectedSeries);
         }
@@ -455,7 +455,7 @@ public class MultiTsFileDeviceIterator implements AutoCloseable {
     }
 
     public boolean hasNextSeries() {
-      if (seriesInThisIteration.size() == 0 && !collectSeries()) {
+      if (seriesInThisIteration.isEmpty() && !collectSeries()) {
         return false;
       } else {
         return true;

server/src/main/java/org/apache/iotdb/db/engine/compaction/execute/utils/executor/fast/AlignedSeriesCompactionExecutor.java

@@ -185,7 +185,7 @@ public class AlignedSeriesCompactionExecutor extends SeriesCompactionExecutor {
         ModificationUtils.modifyAlignedChunkMetaData(alignedChunkMetadataList, valueModifications);
       }
 
-      if (alignedChunkMetadataList.size() == 0) {
+      if (alignedChunkMetadataList.isEmpty()) {
         // all chunks has been deleted in this file or current file does not contain this aligned
         // device, just remove it
         removeFile(fileElement);

server/src/main/java/org/apache/iotdb/db/engine/compaction/execute/utils/executor/fast/SeriesCompactionExecutor.java

@@ -87,7 +87,7 @@ public abstract class SeriesCompactionExecutor {
   // added into this list.
   private final List<PageElement> candidateOverlappedPages = new ArrayList<>();
 
-  public SeriesCompactionExecutor(
+  protected SeriesCompactionExecutor(
       AbstractCompactionWriter compactionWriter,
       Map<TsFileResource, TsFileSequenceReader> readerCacheMap,
       Map<TsFileResource, List<Modification>> modificationCacheMap,
@@ -379,11 +379,9 @@ public abstract class SeriesCompactionExecutor {
     List<PageElement> elements = new ArrayList<>();
     long endTime = page.pageHeader.getEndTime();
     for (PageElement element : pageQueue) {
-      if (element.startTime <= endTime) {
-        if (!element.isSelected) {
-          elements.add(element);
-          element.isSelected = true;
-        }
+      if (element.startTime <= endTime && !element.isSelected) {
+        elements.add(element);
+        element.isSelected = true;
       }
     }
     elements.sort(Comparator.comparingLong(o -> o.startTime));
@@ -400,11 +398,9 @@ public abstract class SeriesCompactionExecutor {
     List<ChunkMetadataElement> elements = new ArrayList<>();
     long endTime = chunkMetadataElement.chunkMetadata.getEndTime();
     for (ChunkMetadataElement element : chunkMetadataQueue) {
-      if (element.chunkMetadata.getStartTime() <= endTime) {
-        if (!element.isSelected) {
-          elements.add(element);
-          element.isSelected = true;
-        }
+      if (element.chunkMetadata.getStartTime() <= endTime && !element.isSelected) {
+        elements.add(element);
+        element.isSelected = true;
       }
     }
     elements.sort(Comparator.comparingLong(o -> o.startTime));

server/src/main/java/org/apache/iotdb/db/engine/compaction/execute/utils/executor/readchunk/SingleSeriesCompactionExecutor.java

@@ -124,7 +124,8 @@ public class SingleSeriesCompactionExecutor {
           constructChunkWriterFromReadChunk(currentChunk);
         }
         CompactionMetricsRecorder.recordReadInfo(
-            currentChunk.getHeader().getSerializedSize() + currentChunk.getHeader().getDataSize());
+            (long) currentChunk.getHeader().getSerializedSize()
+                + currentChunk.getHeader().getDataSize());
 
         // if this chunk is modified, deserialize it into points
         if (chunkMetadata.getDeleteIntervalList() != null) {
@@ -170,7 +171,7 @@ public class SingleSeriesCompactionExecutor {
   }
 
   private long getChunkSize(Chunk chunk) {
-    return chunk.getHeader().getSerializedSize() + chunk.getHeader().getDataSize();
+    return (long) chunk.getHeader().getSerializedSize() + chunk.getHeader().getDataSize();
   }
 
   private void processModifiedChunk(Chunk chunk) throws IOException {

server/src/main/java/org/apache/iotdb/db/engine/compaction/execute/utils/writer/AbstractCrossCompactionWriter.java

@@ -62,7 +62,7 @@ public abstract class AbstractCrossCompactionWriter extends AbstractCompactionWr
 
   protected List<TsFileResource> targetResources;
 
-  public AbstractCrossCompactionWriter(
+  protected AbstractCrossCompactionWriter(
       List<TsFileResource> targetResources, List<TsFileResource> seqFileResources)
       throws IOException {
     currentDeviceEndTime = new long[seqFileResources.size()];

server/src/main/java/org/apache/iotdb/db/engine/compaction/execute/utils/writer/AbstractInnerCompactionWriter.java

@@ -42,7 +42,7 @@ public abstract class AbstractInnerCompactionWriter extends AbstractCompactionWr
   protected long targetPagePointNum =
       TSFileDescriptor.getInstance().getConfig().getMaxNumberOfPointsInPage();
 
-  public AbstractInnerCompactionWriter(TsFileResource targetFileResource) throws IOException {
+  protected AbstractInnerCompactionWriter(TsFileResource targetFileResource) throws IOException {
     long sizeForFileWriter =
         (long)
             (SystemInfo.getInstance().getMemorySizeForCompaction()

server/src/main/java/org/apache/iotdb/db/engine/compaction/selector/ICrossSpaceSelector.java

@@ -24,6 +24,7 @@ import org.apache.iotdb.db.engine.storagegroup.TsFileResource;
 import java.util.List;
 
 public interface ICrossSpaceSelector extends ICompactionSelector {
+  @Override
   List<CrossCompactionTaskResource> selectCrossSpaceTask(
       List<TsFileResource> seqFiles, List<TsFileResource> unseqFiles);
 }

server/src/main/java/org/apache/iotdb/db/engine/compaction/selector/IInnerSeqSpaceSelector.java

@@ -23,5 +23,6 @@ import org.apache.iotdb.db.engine.storagegroup.TsFileResource;
 import java.util.List;
 
 public interface IInnerSeqSpaceSelector extends ICompactionSelector {
+  @Override
   List<List<TsFileResource>> selectInnerSpaceTask(List<TsFileResource> resources);
 }

server/src/main/java/org/apache/iotdb/db/engine/compaction/selector/IInnerUnseqSpaceSelector.java

@@ -23,5 +23,6 @@ import org.apache.iotdb.db.engine.storagegroup.TsFileResource;
 import java.util.List;
 
 public interface IInnerUnseqSpaceSelector extends ICompactionSelector {
+  @Override
   List<List<TsFileResource>> selectInnerSpaceTask(List<TsFileResource> resources);
 }

server/src/main/java/org/apache/iotdb/db/engine/compaction/selector/impl/RewriteCrossSpaceCompactionSelector.java

@@ -72,9 +72,8 @@ public class RewriteCrossSpaceCompactionSelector implements ICrossSpaceSelector
     this.tsFileManager = tsFileManager;
     this.memoryBudget =
         (long)
-            ((double)
-                    (SystemInfo.getInstance().getMemorySizeForCompaction()
-                        / IoTDBDescriptor.getInstance().getConfig().getCompactionThreadCount())
+            ((double) SystemInfo.getInstance().getMemorySizeForCompaction()
+                / IoTDBDescriptor.getInstance().getConfig().getCompactionThreadCount()
                 * config.getUsableCompactionMemoryProportion());
     this.maxCrossCompactionFileNum =
         IoTDBDescriptor.getInstance().getConfig().getMaxCrossCompactionCandidateFileNum();
@@ -190,7 +189,7 @@ public class RewriteCrossSpaceCompactionSelector implements ICrossSpaceSelector
       long memoryCost) {
     // currently, we must allow at least one unseqFile be selected to handle the situation that
     // an unseqFile has huge time range but few data points.
-    if (taskResource.getUnseqFiles().size() == 0) {
+    if (taskResource.getUnseqFiles().isEmpty()) {
       return true;
     }
     long totalFileSize = unseqFile.getTsFileSize();

server/src/main/java/org/apache/iotdb/db/engine/load/LoadTsFileManager.java

@@ -145,7 +145,7 @@ public class LoadTsFileManager {
     uuid2Future.remove(uuid);
 
     if (loadDir.delete()) { // this method will check if there sub-dir in this dir.
-      logger.info(String.format("Delete load dir %s.", loadDir.getPath()));
+      logger.info("Delete load dir {}.", loadDir.getPath());
     }
   }
 
@@ -155,7 +155,7 @@ public class LoadTsFileManager {
     uuid2Future.remove(uuid);
 
     if (loadDir.delete()) { // this method will check if there sub-dir in this dir.
-      logger.info(String.format("Delete load dir %s.", loadDir.getPath()));
+      logger.info("Delete load dir {}.", loadDir.getPath());
     }
   }
 
@@ -179,7 +179,7 @@ public class LoadTsFileManager {
         FileUtils.deleteDirectory(dir);
       }
       if (dir.mkdirs()) {
-        logger.info(String.format("Load TsFile dir %s is created.", dir.getPath()));
+        logger.info("Load TsFile dir {} is created.", dir.getPath());
       }
     }
 
@@ -192,7 +192,7 @@ public class LoadTsFileManager {
             SystemFileFactory.INSTANCE.getFile(
                 taskDir, partitionInfo.toString() + TsFileConstant.TSFILE_SUFFIX);
         if (!newTsFile.createNewFile()) {
-          logger.error(String.format("Can not create TsFile %s for writing.", newTsFile.getPath()));
+          logger.error("Can not create TsFile {} for writing.", newTsFile.getPath());
           return;
         }
 
@@ -250,7 +250,7 @@ public class LoadTsFileManager {
               writer.close();
             }
             if (writer.getFile().exists() && !writer.getFile().delete()) {
-              logger.warn(String.format("Delete File %s error.", writer.getFile()));
+              logger.warn("Delete File {} error.", writer.getFile());
             }
           } catch (IOException e) {
             logger.warn(
@@ -261,7 +261,7 @@ public class LoadTsFileManager {
         }
       }
       if (!taskDir.delete()) {
-        logger.warn(String.format("Can not delete load dir %s.", taskDir.getPath()));
+        logger.warn("Can not delete load dir {}.", taskDir.getPath());
       }
       dataPartition2Writer = null;
       dataPartition2LastDevice = null;

server/src/main/java/org/apache/iotdb/db/engine/modification/utils/TracedBufferedReader.java

@@ -321,7 +321,7 @@ public class TracedBufferedReader extends Reader {
             nextChar++;
           }
         }
-        long d = nChars - nextChar;
+        long d = (long) nChars - nextChar;
         if (r <= d) {
           nextChar += r;
           r = 0;

server/src/main/java/org/apache/iotdb/db/engine/storagegroup/DataRegion.java

@@ -3169,7 +3169,7 @@ public class DataRegion implements IDataRegionForQuery {
       List<TsFileResource> seqResourcesToBeSettled,
       List<TsFileResource> unseqResourcesToBeSettled,
       List<String> tsFilePaths) {
-    if (tsFilePaths.size() == 0) {
+    if (tsFilePaths.isEmpty()) {
       for (TsFileResource resource : tsFileManager.getTsFileList(true)) {
         if (!resource.isClosed()) {
           continue;

server/src/main/java/org/apache/iotdb/db/engine/trigger/sink/forward/ForwardEvent.java

@@ -64,6 +64,7 @@ public class ForwardEvent implements Event {
     return value;
   }
 
+  @Override
   public PartialPath getFullPath() {
     return fullPath;
   }

server/src/main/java/org/apache/iotdb/db/engine/trigger/utils/BatchHandlerQueue.java

@@ -112,6 +112,7 @@ public class BatchHandlerQueue<T extends Event> {
       this.queue = queue;
     }
 
+    @Override
     public void run() {
       final long maxWaitMillis = 500;
       final ArrayList<T> list = new ArrayList<>();