code: /*
   * 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;
  
  /**
   * Reverses the result of comparing two objects using
   * the delegate {@link Comparator}.
   *
   * @version $Revision: 1.1.2.1.2.1 $ $Date: 2011/01/15 20:32:24 $
   * @since Commons IO 1.4
   */
  class ReverseComparator extends AbstractFileComparator implements Serializable {
  
      private final Comparator<File> delegate;
  
      /**
       * Construct an instance with the sepecified delegate {@link Comparator}.
       *
       * @param delegate The comparator to delegate to
       */
      public ReverseComparator(Comparator<File> delegate) {
          if (delegate == null) {
              throw new IllegalArgumentException("Delegate comparator is missing");
          }
          this.delegate = delegate;
      }
  
      /**
       * Compare using the delegate Comparator, but 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)
       */
      public int compare(File file1, File file2) {
          return delegate.compare(file2, file1); // parameters switched round
      }
  
      /**
       * String representation of this file comparator.
       *
       * @return String representation of this file comparator
       */
      @Override
      public String toString() {
          return super.toString() + "[" + delegate.toString() + "]";
      }
  
  }
  