Commons IO example source code file (ReverseComparator.java)

This example Commons IO source code file (ReverseComparator.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Commons IO tags/keywords

abstractfilecomparator, comparator, comparator, delegate, file, file, illegalargumentexception, io, override, reversecomparator, reversecomparator, serializable, serializable, string, util

The Commons IO ReverseComparator.java source 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: 1021884 $ $Date: 2010-10-12 19:49:16 +0100 (Tue, 12 Oct 2010) $
 * @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() + "]";
    }

}