Add new ComposableFileFilter extension and implementation of Java's FileFilter interface.

Author: jxblum

spring-data-geode-test/src/main/java/org/springframework/data/gemfire/tests/util/ComposableFileFilter.java

@@ -0,0 +1,44 @@
+/*
+ *  Copyright 2017-present 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.
+ *  You may obtain a copy of the License at
+ *
+ *       https://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+ *  or implied. See the License for the specific language governing
+ *  permissions and limitations under the License.
+ */
+package org.springframework.data.gemfire.tests.util;
+
+import java.io.FileFilter;
+
+import org.springframework.lang.NonNull;
+import org.springframework.lang.Nullable;
+
+/**
+ * Java {@link FileFilter} implementation capable of being composed
+ *
+ * @author John Blum
+ * @see java.lang.FunctionalInterface
+ * @see java.io.FileFilter
+ * @since 0.3.5-RAJ
+ */
+@FunctionalInterface
+@SuppressWarnings("unused")
+public interface ComposableFileFilter extends FileFilter {
+
+	default @NonNull ComposableFileFilter andThen(@Nullable ComposableFileFilter fileFilter) {
+		return fileFilter == null ? this
+			: file -> this.accept(file) && fileFilter.accept(file);
+	}
+
+	default @NonNull ComposableFileFilter orThen(@Nullable ComposableFileFilter fileFilter) {
+		return fileFilter == null ? this
+			: file -> this.accept(file) || fileFilter.accept(file);
+	}
+}

spring-data-geode-test/src/main/java/org/springframework/data/gemfire/tests/util/FileSystemUtils.java

@@ -121,9 +121,7 @@ public static boolean isEmpty(@Nullable File path) {
 
 		File[] files = isDirectory(directory) ? directory.listFiles(resolvedFileFilter) : null;
 
-		return files != null
-			? files
-			: NO_FILES;
+		return files != null ? files : NO_FILES;
 	}
 
 	public static class AllFilesFilter implements FileFilter {