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 *      http://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.Comparator;
022import java.util.stream.Stream;
023import java.util.stream.StreamSupport;
024
025/**
026 * Compare two files using a set of delegate file {@link Comparator}.
027 * <p>
028 * This comparator can be used to sort lists or arrays of files by combining a number of other comparators.
029 * <p>
030 * Example of sorting a list of files by type (i.e. directory or file) and then by name:
031 *
032 * <pre>
033 *       CompositeFileComparator comparator = new CompositeFileComparator(
034 *           DirectoryFileComparator.DIRECTORY_COMPARATOR,
035 *           NameFileComparator.NAME_COMPARATOR);
036 *       List&lt;File&gt; list = ...
037 *       comparator.sort(list);
038 * </pre>
039 * <h2>Deprecating Serialization</h2>
040 * <p>
041 * <em>Serialization is deprecated and will be removed in 3.0.</em>
042 * </p>
043 *
044 * @since 2.0
045 */
046public class CompositeFileComparator extends AbstractFileComparator implements Serializable {
047
048    private static final Comparator<?>[] EMPTY_COMPARATOR_ARRAY = {};
049    private static final long serialVersionUID = -2224170307287243428L;
050
051    private final Comparator<File>[] delegates;
052
053    /**
054     * Constructs a composite comparator for the set of delegate comparators.
055     *
056     * @param delegates The delegate file comparators
057     */
058    public CompositeFileComparator(@SuppressWarnings("unchecked") final Comparator<File>... delegates) {
059        this.delegates = delegates == null ? emptyArray() : delegates.clone();
060    }
061
062    /**
063     * Constructs a composite comparator for the set of delegate comparators.
064     *
065     * @param delegates The delegate file comparators
066     */
067    public CompositeFileComparator(final Iterable<Comparator<File>> delegates) {
068        this.delegates = delegates == null ? emptyArray() : StreamSupport.stream(delegates.spliterator(), false).toArray(Comparator[]::new);
069    }
070
071    /**
072     * Compares the two files using delegate comparators.
073     *
074     * @param file1 The first file to compare
075     * @param file2 The second file to compare
076     * @return the first non-zero result returned from the delegate comparators or zero.
077     */
078    @Override
079    public int compare(final File file1, final File file2) {
080        return Stream.of(delegates).map(delegate -> delegate.compare(file1, file2)).filter(r -> r != 0).findFirst().orElse(0);
081    }
082
083    @SuppressWarnings("unchecked") // types are already correct
084    private Comparator<File>[] emptyArray() {
085        return (Comparator<File>[]) EMPTY_COMPARATOR_ARRAY;
086    }
087
088    /**
089     * String representation of this file comparator.
090     *
091     * @return String representation of this file comparator
092     */
093    @Override
094    public String toString() {
095        final StringBuilder builder = new StringBuilder();
096        builder.append(super.toString());
097        builder.append('{');
098        for (int i = 0; i < delegates.length; i++) {
099            if (i > 0) {
100                builder.append(',');
101            }
102            builder.append(delegates[i]);
103        }
104        builder.append('}');
105        return builder.toString();
106    }
107}