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 = {};
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}