diff --git a/dolphinscheduler-api/src/main/java/org/apache/dolphinscheduler/api/service/WorkerGroupService.java b/dolphinscheduler-api/src/main/java/org/apache/dolphinscheduler/api/service/WorkerGroupService.java
index c44c446d5c..7d47a8fb0d 100644
--- a/dolphinscheduler-api/src/main/java/org/apache/dolphinscheduler/api/service/WorkerGroupService.java
+++ b/dolphinscheduler-api/src/main/java/org/apache/dolphinscheduler/api/service/WorkerGroupService.java
@@ -111,7 +111,7 @@ public class WorkerGroupService extends BaseService {
 
         List<WorkerGroup> workerGroupList = workerGroupMapper.queryWorkerGroupByName(workerGroup.getName());
 
-        if(workerGroupList.size() > 0 ){
+        if(CollectionUtils.isNotEmpty(workerGroupList)){
             // new group has same name..
             if(workerGroup.getId() == 0){
                 return true;
diff --git a/dolphinscheduler-dao/src/test/java/org/apache/dolphinscheduler/dao/mapper/WorkerGroupMapperTest.java b/dolphinscheduler-dao/src/test/java/org/apache/dolphinscheduler/dao/mapper/WorkerGroupMapperTest.java
index ea05f1bf11..dfa2a5de8e 100644
--- a/dolphinscheduler-dao/src/test/java/org/apache/dolphinscheduler/dao/mapper/WorkerGroupMapperTest.java
+++ b/dolphinscheduler-dao/src/test/java/org/apache/dolphinscheduler/dao/mapper/WorkerGroupMapperTest.java
@@ -65,7 +65,7 @@ public class WorkerGroupMapperTest {
         workerGroup.setName("workerGroup11");
         int update = workerGroupMapper.updateById(workerGroup);
         workerGroupMapper.deleteById(workerGroup.getId());
-        Assert.assertEquals(update, 1);
+        Assert.assertEquals(1, update);
     }
 
     /**
@@ -77,7 +77,7 @@ public class WorkerGroupMapperTest {
         WorkerGroup workerGroup = insertOne();
         //delete
         int delete = workerGroupMapper.deleteById(workerGroup.getId());
-        Assert.assertEquals(delete, 1);
+        Assert.assertEquals(1, delete);
     }
 
     /**
diff --git a/dolphinscheduler-server/src/main/java/org/apache/dolphinscheduler/server/worker/WorkerServer.java b/dolphinscheduler-server/src/main/java/org/apache/dolphinscheduler/server/worker/WorkerServer.java
index 86bb7d3e07..868b80960f 100644
--- a/dolphinscheduler-server/src/main/java/org/apache/dolphinscheduler/server/worker/WorkerServer.java
+++ b/dolphinscheduler-server/src/main/java/org/apache/dolphinscheduler/server/worker/WorkerServer.java
@@ -52,7 +52,6 @@ import org.springframework.context.annotation.FilterType;
 import javax.annotation.PostConstruct;
 import javax.annotation.PreDestroy;
 import java.util.Set;
-import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
@@ -255,7 +254,7 @@ public class WorkerServer implements IStoppable {
      */
     private Runnable heartBeatThread(){
         logger.info("start worker heart beat thread...");
-        Runnable heartBeatThread  = new Runnable() {
+        return new Runnable() {
             @Override
             public void run() {
                 // send heartbeat to zk
@@ -266,7 +265,6 @@ public class WorkerServer implements IStoppable {
                 zkWorkerClient.heartBeatForZk(zkWorkerClient.getWorkerZNode() , Constants.WORKER_PREFIX);
             }
         };
-        return heartBeatThread;
     }
 
 
@@ -276,7 +274,7 @@ public class WorkerServer implements IStoppable {
      * @return kill process thread
      */
     private Runnable getKillProcessThread(){
-        Runnable killProcessThread  = new Runnable() {
+        return new Runnable() {
             @Override
             public void run() {
                 logger.info("start listening kill process thread...");
@@ -297,7 +295,6 @@ public class WorkerServer implements IStoppable {
                 }
             }
         };
-        return killProcessThread;
     }
 
     /**
@@ -307,17 +304,17 @@ public class WorkerServer implements IStoppable {
      * @param pd        process dao
      */
     private void killTask(String taskInfo, ProcessService pd) {
-        logger.info("get one kill command from tasks kill queue: " + taskInfo);
+        logger.info("get one kill command from tasks kill queue: {}" , taskInfo);
         String[] taskInfoArray = taskInfo.split("-");
         if(taskInfoArray.length != 2){
-            logger.error("error format kill info: " + taskInfo);
+            logger.error("error format kill info: {}", taskInfo);
             return ;
         }
         String host = taskInfoArray[0];
         int taskInstanceId = Integer.parseInt(taskInfoArray[1]);
         TaskInstance taskInstance = pd.getTaskInstanceDetailByTaskId(taskInstanceId);
         if(taskInstance == null){
-            logger.error("cannot find the kill task :" + taskInfo);
+            logger.error("cannot find the kill task : {}", taskInfo);
             return;
         }
 
@@ -332,8 +329,7 @@ public class WorkerServer implements IStoppable {
             }else if(!taskInstance.getState().typeIsFinished()){
                 ProcessUtils.kill(taskInstance);
             }else{
-                logger.info("the task aleady finish: task id: " + taskInstance.getId()
-                        + " state: " + taskInstance.getState().toString());
+                logger.info("the task aleady finish: task id: {} state: {}", taskInstance.getId(), taskInstance.getState());
             }
         }
     }
@@ -347,7 +343,7 @@ public class WorkerServer implements IStoppable {
     private void deleteTaskFromQueue(TaskInstance taskInstance, ProcessService pd){
         // creating distributed locks, lock path /dolphinscheduler/lock/worker
         InterProcessMutex mutex = null;
-        logger.info("delete task from tasks queue: " + taskInstance.getId());
+        logger.info("delete task from tasks queue: {}", taskInstance.getId());
 
         try {
             mutex = zkWorkerClient.acquireZkLock(zkWorkerClient.getZkClient(),