Add @nullable to StepExecution::getEndTime

Author: acktsap

spring-batch-core/src/main/java/org/springframework/batch/core/StepExecution.java

@@ -24,6 +24,7 @@
 import java.util.concurrent.CopyOnWriteArrayList;
 
 import org.springframework.batch.item.ExecutionContext;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -34,6 +35,7 @@
  * @author Lucas Ward
  * @author Dave Syer
  * @author Mahmoud Ben Hassine
+ * @author Taeik Lim
  *
  */
 @SuppressWarnings("serial")
@@ -159,6 +161,7 @@ public void setCommitCount(long commitCount) {
 	 *
 	 * @return the time that this execution ended
 	 */
+	@Nullable
 	public Date getEndTime() {
 		return endTime;
 	}