    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.function.IntFunction;
    023import java.util.stream.Stream;
    024import java.util.stream.StreamSupport;
    025
    026/**
    027 * Compare two files using a set of delegate file {@link Comparator}.
    028 * <p>
    029 * This comparator can be used to sort lists or arrays of files by combining a number of other comparators.
    030 * <p>
    031 * Example of sorting a list of files by type (i.e. directory or file) and then by name:
    032 *
    033 * <pre>
    034 *       CompositeFileComparator comparator = new CompositeFileComparator(
    035 *           DirectoryFileComparator.DIRECTORY_COMPARATOR,
    036 *           NameFileComparator.NAME_COMPARATOR);
    037 *       List&lt;File&gt; list = ...
    038 *       comparator.sort(list);
    039 * </pre>
    040 * <h2>Deprecating Serialization</h2>
    041 * <p>
    042 * <em>Serialization is deprecated and will be removed in 3.0.</em>
    043 * </p>
    044 *
    045 * @since 2.0
    046 */
    047public class CompositeFileComparator extends AbstractFileComparator implements Serializable {
    048
    049    private static final Comparator<?>[] EMPTY_COMPARATOR_ARRAY = {};
    050    private static final long serialVersionUID = -2224170307287243428L;
    051
    052    /**
    053     * Delegates.
    054     */
    055    private final Comparator<File>[] delegates;
    056
    057    /**
    058     * Constructs a composite comparator for the set of delegate comparators.
    059     *
    060     * @param delegates The delegate file comparators
    061     */
    062    public CompositeFileComparator(@SuppressWarnings("unchecked") final Comparator<File>... delegates) {
    063        this.delegates = delegates == null ? emptyArray() : delegates.clone();
    064    }
    065
    066    /**
    067     * Constructs a composite comparator for the set of delegate comparators.
    068     *
    069     * @param delegates The delegate file comparators
    070     */
    071    public CompositeFileComparator(final Iterable<Comparator<File>> delegates) {
    072        this.delegates = delegates == null ? emptyArray()
    073                : StreamSupport.stream(delegates.spliterator(), false).toArray((IntFunction<Comparator<File>[]>) Comparator[]::new);
    074    }
    075
    076    /**
    077     * Compares the two files using delegate comparators.
    078     *
    079     * @param file1 The first file to compare
    080     * @param file2 The second file to compare
    081     * @return the first non-zero result returned from the delegate comparators or zero.
    082     */
    083    @Override
    084    public int compare(final File file1, final File file2) {
    085        return Stream.of(delegates).map(delegate -> delegate.compare(file1, file2)).filter(r -> r != 0).findFirst().orElse(0);
    086    }
    087
    088    @SuppressWarnings("unchecked") // types are already correct
    089    private Comparator<File>[] emptyArray() {
    090        return (Comparator<File>[]) EMPTY_COMPARATOR_ARRAY;
    091    }
    092
    093    /**
    094     * String representation of this file comparator.
    095     *
    096     * @return String representation of this file comparator
    097     */
    098    @Override
    099    public String toString() {
    100        final StringBuilder builder = new StringBuilder();
    101        builder.append(super.toString());
    102        builder.append('{');
    103        for (int i = 0; i < delegates.length; i++) {
    104            if (i > 0) {
    105                builder.append(',');
    106            }
    107            builder.append(delegates[i]);
    108        }
    109        builder.append('}');
    110        return builder.toString();
    111    }
    112}