1 files changed, 66 insertions, 0 deletions
diff --git a/src/main/java/org/apache/commons/io/comparator/ReverseFileComparator.java b/src/main/java/org/apache/commons/io/comparator/ReverseFileComparator.java
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+++ b/src/main/java/org/apache/commons/io/comparator/ReverseFileComparator.java
@@ -0,0 +1,66 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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
+ *
+ *      http://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.apache.commons.io.comparator;
+
+import java.io.File;
+import java.io.Serializable;
+import java.util.Comparator;
+import java.util.Objects;
+
+/**
+ * Reverses the result of comparing two {@link File} objects using the delegate {@link Comparator}.
+ *
+ * @since 1.4
+ */
+class ReverseFileComparator extends AbstractFileComparator implements Serializable {
+
+    private static final long serialVersionUID = -4808255005272229056L;
+    private final Comparator<File> delegate;
+
+    /**
+     * Constructs an instance with the specified delegate {@link Comparator}.
+     *
+     * @param delegate The comparator to delegate to.
+     */
+    public ReverseFileComparator(final Comparator<File> delegate) {
+        this.delegate = Objects.requireNonNull(delegate, "delegate");
+    }
+
+    /**
+     * Compares using the delegate Comparator, reversing the result.
+     *
+     * @param file1 The first file to compare.
+     * @param file2 The second file to compare.
+     * @return the result from the delegate {@link Comparator#compare(Object, Object)} reversing the value (i.e.
+     *         positive becomes negative and vice versa).
+     */
+    @Override
+    public int compare(final File file1, final File file2) {
+        return delegate.compare(file2, file1); // parameters switched round
+    }
+
+    /**
+     * Returns the String representation of this file comparator.
+     *
+     * @return String representation of this file comparator.
+     */
+    @Override
+    public String toString() {
+        return super.toString() + "[" + delegate.toString() + "]";
+    }
+
+}