* Improve generics handling for FileUtils

Author: artembilan

spring-integration-file/src/main/java/org/springframework/integration/file/remote/AbstractRemoteFileStreamingMessageSource.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2021 the original author or authors.
+ * Copyright 2016-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -62,11 +62,11 @@
 public abstract class AbstractRemoteFileStreamingMessageSource<F>
 		extends AbstractFetchLimitingMessageSource<InputStream> implements ManageableLifecycle {
 
-	private final RemoteFileTemplate<F> remoteFileTemplate;
+	private final RemoteFileTemplate<? extends F> remoteFileTemplate;
 
 	private final BlockingQueue<AbstractFileInfo<F>> toBeReceived = new LinkedBlockingQueue<>();
 
-	private final Comparator<F> comparator;
+	private final Comparator<? extends F> comparator;
 
 	private final AtomicBoolean running = new AtomicBoolean();
 
@@ -86,8 +86,8 @@ public abstract class AbstractRemoteFileStreamingMessageSource<F>
 	 */
 	private FileListFilter<F> filter;
 
-	protected AbstractRemoteFileStreamingMessageSource(RemoteFileTemplate<F> template,
-			@Nullable Comparator<F> comparator) {
+	protected AbstractRemoteFileStreamingMessageSource(RemoteFileTemplate<? extends F> template,
+			@Nullable Comparator<? extends F> comparator) {
 
 		Assert.notNull(template, "'template' must not be null");
 		this.remoteFileTemplate = template;
@@ -143,7 +143,7 @@ public void setFileInfoJson(boolean fileInfoJson) {
 		this.fileInfoJson = fileInfoJson;
 	}
 
-	protected RemoteFileTemplate<F> getRemoteFileTemplate() {
+	protected RemoteFileTemplate<? extends F> getRemoteFileTemplate() {
 		return this.remoteFileTemplate;
 	}
 

spring-integration-file/src/main/java/org/springframework/integration/file/remote/synchronizer/AbstractInboundFileSynchronizer.java

@@ -123,7 +123,7 @@ public abstract class AbstractInboundFileSynchronizer<F>
 	private BeanFactory beanFactory;
 
 	@Nullable
-	private Comparator<F> comparator;
+	private Comparator<? extends F> comparator;
 
 	private MetadataStore remoteFileMetadataStore = new SimpleMetadataStore();
 
@@ -141,7 +141,7 @@ public AbstractInboundFileSynchronizer(SessionFactory<F> sessionFactory) {
 	}
 
 	@Nullable
-	protected Comparator<F> getComparator() {
+	protected Comparator<? extends F> getComparator() {
 		return this.comparator;
 	}
 
@@ -151,9 +151,8 @@ protected Comparator<F> getComparator() {
 	 * @param comparator the comparator.
 	 * @since 5.1
 	 */
-	@SuppressWarnings("unchecked")
 	public void setComparator(@Nullable Comparator<? extends F> comparator) {
-		this.comparator = (Comparator<F>) comparator;
+		this.comparator = comparator;
 	}
 
 	/**

spring-integration-file/src/main/java/org/springframework/integration/file/support/FileUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2017-2019 the original author or authors.
+ * Copyright 2017-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -29,6 +29,7 @@
  * Utilities for operations on Files.
  *
  * @author Gary Russell
+ * @author Artem Bilan
  *
  * @since 5.0
  *
@@ -47,22 +48,22 @@ public final class FileUtils {
 	 * @since 5.0.7
 	 */
 	@SuppressWarnings("unchecked")
-	public static <F> F[] purgeUnwantedElements(F[] fileArray, Predicate<F> predicate,
-			@Nullable Comparator<F> comparator) {
+	public static <F> F[] purgeUnwantedElements(F[] fileArray, Predicate<? extends F> predicate,
+			@Nullable Comparator<? extends F> comparator) {
 
 		if (ObjectUtils.isEmpty(fileArray)) {
 			return fileArray;
 		}
 		else {
 			if (comparator == null) {
 				return Arrays.stream(fileArray)
-						.filter(predicate.negate())
+						.filter((Predicate<? super F>) predicate.negate())
 						.toArray(size -> (F[]) Array.newInstance(fileArray[0].getClass(), size));
 			}
 			else {
 				return Arrays.stream(fileArray)
-						.filter(predicate.negate())
-						.sorted(comparator)
+						.filter((Predicate<? super F>) predicate.negate())
+						.sorted((Comparator<? super F>) comparator)
 						.toArray(size -> (F[]) Array.newInstance(fileArray[0].getClass(), size));
 			}
 		}