diff --git a/spring-cloud-task-batch/src/main/java/org/springframework/cloud/task/batch/partition/DeployerPartitionHandler.java b/spring-cloud-task-batch/src/main/java/org/springframework/cloud/task/batch/partition/DeployerPartitionHandler.java
index 1cfa92d1..a4f6704b 100644
--- a/spring-cloud-task-batch/src/main/java/org/springframework/cloud/task/batch/partition/DeployerPartitionHandler.java
+++ b/spring-cloud-task-batch/src/main/java/org/springframework/cloud/task/batch/partition/DeployerPartitionHandler.java
@@ -17,6 +17,7 @@ package org.springframework.cloud.task.batch.partition;
 
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
@@ -246,7 +247,7 @@ public class DeployerPartitionHandler implements PartitionHandler, EnvironmentAw
 		final Set<StepExecution> executed = new HashSet<>(candidates.size());
 
 		if (CollectionUtils.isEmpty(candidates)) {
-			return null;
+			return Collections.emptySet();
 		}
 
 		launchWorkers(candidates, executed);
diff --git a/spring-cloud-task-batch/src/test/java/org/springframework/cloud/task/batch/partition/DeployerPartitionHandlerTests.java b/spring-cloud-task-batch/src/test/java/org/springframework/cloud/task/batch/partition/DeployerPartitionHandlerTests.java
index 3315da37..298e3821 100644
--- a/spring-cloud-task-batch/src/test/java/org/springframework/cloud/task/batch/partition/DeployerPartitionHandlerTests.java
+++ b/spring-cloud-task-batch/src/test/java/org/springframework/cloud/task/batch/partition/DeployerPartitionHandlerTests.java
@@ -111,7 +111,7 @@ public class DeployerPartitionHandlerTests {
 		Collection<StepExecution> results = handler.handle(this.splitter, stepExecution);
 
 		verify(this.taskLauncher, never()).launch((AppDeploymentRequest) any());
-		assertNull(results);
+		assertTrue(results.isEmpty());
 	}
 
 	@Test
diff --git a/spring-cloud-task-core/src/main/java/org/springframework/cloud/task/repository/dao/JdbcTaskExecutionDao.java b/spring-cloud-task-core/src/main/java/org/springframework/cloud/task/repository/dao/JdbcTaskExecutionDao.java
index eabb442e..c73a177f 100644
--- a/spring-cloud-task-core/src/main/java/org/springframework/cloud/task/repository/dao/JdbcTaskExecutionDao.java
+++ b/spring-cloud-task-core/src/main/java/org/springframework/cloud/task/repository/dao/JdbcTaskExecutionDao.java
@@ -325,8 +325,9 @@ public class JdbcTaskExecutionDao implements TaskExecutionDao {
 	public long getRunningTaskExecutionCount() {
 
 		try {
+			final MapSqlParameterSource queryParameters = new MapSqlParameterSource();
 			return jdbcTemplate.queryForObject(
-				getQuery(RUNNING_TASK_EXECUTION_COUNT), (SqlParameterSource)null, Long.class);
+				getQuery(RUNNING_TASK_EXECUTION_COUNT), queryParameters, Long.class);
 		}
 		catch (EmptyResultDataAccessException e) {
 			return 0;
diff --git a/spring-cloud-task-core/src/main/java/org/springframework/cloud/task/repository/dao/MapTaskExecutionDao.java b/spring-cloud-task-core/src/main/java/org/springframework/cloud/task/repository/dao/MapTaskExecutionDao.java
index c148ea63..16b51942 100644
--- a/spring-cloud-task-core/src/main/java/org/springframework/cloud/task/repository/dao/MapTaskExecutionDao.java
+++ b/spring-cloud-task-core/src/main/java/org/springframework/cloud/task/repository/dao/MapTaskExecutionDao.java
@@ -322,7 +322,7 @@ public class MapTaskExecutionDao implements TaskExecutionDao {
 		}
 	}
 
-	private class TaskExecutionComparator implements Comparator<TaskExecution> {
+	private static class TaskExecutionComparator implements Comparator<TaskExecution> {
 		@Override
 		public int compare(TaskExecution firstTaskExecution, TaskExecution secondTaskExecution) {
 			if (firstTaskExecution.getStartTime().equals(secondTaskExecution.getStartTime())) {
diff --git a/spring-cloud-task-samples/timestamp/src/main/java/org/springframework/cloud/task/timestamp/TaskApplication.java b/spring-cloud-task-samples/timestamp/src/main/java/org/springframework/cloud/task/timestamp/TaskApplication.java
index 85296e08..e03e912d 100644
--- a/spring-cloud-task-samples/timestamp/src/main/java/org/springframework/cloud/task/timestamp/TaskApplication.java
+++ b/spring-cloud-task-samples/timestamp/src/main/java/org/springframework/cloud/task/timestamp/TaskApplication.java
@@ -52,7 +52,7 @@ public class TaskApplication {
 	/**
 	 * A commandline runner that prints a timestamp.
 	 */
-	public class TimestampTask implements CommandLineRunner {
+	public static class TimestampTask implements CommandLineRunner {
 
 		@Autowired
 		private TimestampTaskProperties config;
diff --git a/spring-cloud-task-stream/src/main/java/org/springframework/cloud/task/batch/listener/support/JobExecutionEvent.java b/spring-cloud-task-stream/src/main/java/org/springframework/cloud/task/batch/listener/support/JobExecutionEvent.java
index 1262bfbe..4379c40c 100644
--- a/spring-cloud-task-stream/src/main/java/org/springframework/cloud/task/batch/listener/support/JobExecutionEvent.java
+++ b/spring-cloud-task-stream/src/main/java/org/springframework/cloud/task/batch/listener/support/JobExecutionEvent.java
@@ -55,7 +55,7 @@ public class JobExecutionEvent extends Entity {
 
 	private Date lastUpdated = null;
 
-	private ExitStatus exitStatus = new ExitStatus(new org.springframework.batch.core.ExitStatus("UNKNOWN", null));
+	private ExitStatus exitStatus = new ExitStatus(new org.springframework.batch.core.ExitStatus("UNKNOWN"));
 
 	private ExecutionContext executionContext = new ExecutionContext();