001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      https://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.io.comparator;
018
019import java.io.File;
020import java.io.Serializable;
021import java.util.Arrays;
022import java.util.Comparator;
023import java.util.function.IntFunction;
024import java.util.stream.Stream;
025import java.util.stream.StreamSupport;
026
027/**
028 * Compare two files using a set of delegate file {@link Comparator}.
029 * <p>
030 * This comparator can be used to sort lists or arrays of files by combining a number of other comparators.
031 * <p>
032 * Example of sorting a list of files by type (directory or file) and then by name:
033 *
034 * <pre>
035 *       CompositeFileComparator comparator = new CompositeFileComparator(
036 *           DirectoryFileComparator.DIRECTORY_COMPARATOR,
037 *           NameFileComparator.NAME_COMPARATOR);
038 *       List&lt;File&gt; list = ...
039 *       comparator.sort(list);
040 * </pre>
041 * <h2>Deprecating Serialization</h2>
042 * <p>
043 * <em>Serialization is deprecated and will be removed in 3.0.</em>
044 * </p>
045 *
046 * @since 2.0
047 */
048public class CompositeFileComparator extends AbstractFileComparator implements Serializable {
049
050    private static final Comparator<?>[] EMPTY_COMPARATOR_ARRAY = {};
051    private static final long serialVersionUID = -2224170307287243428L;
052
053    /**
054     * Delegates.
055     */
056    private final Comparator<File>[] delegates;
057
058    /**
059     * Constructs a composite comparator for the set of delegate comparators.
060     *
061     * @param delegates The delegate file comparators
062     */
063    public CompositeFileComparator(@SuppressWarnings("unchecked") final Comparator<File>... delegates) {
064        this.delegates = delegates == null ? emptyArray() : delegates.clone();
065    }
066
067    /**
068     * Constructs a composite comparator for the set of delegate comparators.
069     *
070     * @param delegates The delegate file comparators
071     */
072    public CompositeFileComparator(final Iterable<Comparator<File>> delegates) {
073        this.delegates = delegates == null ? emptyArray()
074                : StreamSupport.stream(delegates.spliterator(), false).toArray((IntFunction<Comparator<File>[]>) Comparator[]::new);
075    }
076
077    /**
078     * Compares the two files using delegate comparators.
079     *
080     * @param file1 The first file to compare
081     * @param file2 The second file to compare
082     * @return the first non-zero result returned from the delegate comparators or zero.
083     */
084    @Override
085    public int compare(final File file1, final File file2) {
086        return Stream.of(delegates).map(delegate -> delegate.compare(file1, file2)).filter(r -> r != 0).findFirst().orElse(0);
087    }
088
089    @SuppressWarnings("unchecked") // types are already correct
090    private Comparator<File>[] emptyArray() {
091        return (Comparator<File>[]) EMPTY_COMPARATOR_ARRAY;
092    }
093
094    /**
095     * String representation of this file comparator.
096     *
097     * @return String representation of this file comparator
098     */
099    @Override
100    public String toString() {
101        final StringBuilder builder = new StringBuilder(super.toString());
102        builder.append(Arrays.toString(delegates));
103        return builder.toString();
104    }
105}