    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.ArrayList;
    022import java.util.Comparator;
    023import java.util.List;
    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
    029 * by combining a number other comparators.
    030 * <p>
    031 * Example of sorting a list of files by type (i.e. directory or file)
    032 * and then by name:
    033 * <pre>
    034 *       CompositeFileComparator comparator =
    035 *                       new CompositeFileComparator(
    036 *                                 (AbstractFileComparator) DirectoryFileComparator.DIRECTORY_COMPARATOR,
    037 *                                 (AbstractFileComparator) NameFileComparator.NAME_COMPARATOR);
    038 *       List&lt;File&gt; list = ...
    039 *       comparator.sort(list);
    040 * </pre>
    041 *
    042 * @since 2.0
    043 */
    044public class CompositeFileComparator extends AbstractFileComparator implements Serializable {
    045
    046    private static final Comparator<?>[] EMPTY_COMPARATOR_ARRAY = new Comparator<?>[0];
    047    private static final long serialVersionUID = -2224170307287243428L;
    048    private static final Comparator<?>[] NO_COMPARATORS = {};
    049    private final Comparator<File>[] delegates;
    050
    051    /**
    052     * Create a composite comparator for the set of delegate comparators.
    053     *
    054     * @param delegates The delegate file comparators
    055     */
    056    @SuppressWarnings("unchecked") // casts 1 & 2 must be OK because types are already correct
    057    public CompositeFileComparator(final Comparator<File>... delegates) {
    058        if (delegates == null) {
    059            this.delegates = (Comparator<File>[]) NO_COMPARATORS;//1
    060        } else {
    061            this.delegates = (Comparator<File>[]) new Comparator<?>[delegates.length];//2
    062            System.arraycopy(delegates, 0, this.delegates, 0, delegates.length);
    063        }
    064    }
    065
    066    /**
    067     * Create a composite comparator for the set of delegate comparators.
    068     *
    069     * @param delegates The delegate file comparators
    070     */
    071    @SuppressWarnings("unchecked") // casts 1 & 2 must be OK because types are already correct
    072    public CompositeFileComparator(final Iterable<Comparator<File>> delegates) {
    073        if (delegates == null) {
    074            this.delegates = (Comparator<File>[]) NO_COMPARATORS; //1
    075        } else {
    076            final List<Comparator<File>> list = new ArrayList<>();
    077            for (final Comparator<File> comparator : delegates) {
    078                list.add(comparator);
    079            }
    080            this.delegates = (Comparator<File>[]) list.toArray(EMPTY_COMPARATOR_ARRAY); //2
    081        }
    082    }
    083
    084    /**
    085     * Compare the two files using delegate comparators.
    086     *
    087     * @param file1 The first file to compare
    088     * @param file2 The second file to compare
    089     * @return the first non-zero result returned from
    090     * the delegate comparators or zero.
    091     */
    092    @Override
    093    public int compare(final File file1, final File file2) {
    094        int result = 0;
    095        for (final Comparator<File> delegate : delegates) {
    096            result = delegate.compare(file1, file2);
    097            if (result != 0) {
    098                break;
    099            }
    100        }
    101        return result;
    102    }
    103
    104    /**
    105     * String representation of this file comparator.
    106     *
    107     * @return String representation of this file comparator
    108     */
    109    @Override
    110    public String toString() {
    111        final StringBuilder builder = new StringBuilder();
    112        builder.append(super.toString());
    113        builder.append('{');
    114        for (int i = 0; i < delegates.length; i++) {
    115            if (i > 0) {
    116                builder.append(',');
    117            }
    118            builder.append(delegates[i]);
    119        }
    120        builder.append('}');
    121        return builder.toString();
    122    }
    123}