    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;
    018
    019import java.io.File;
    020import java.io.FileFilter;
    021import java.io.IOException;
    022import java.nio.file.Files;
    023import java.util.Collection;
    024import java.util.Objects;
    025
    026import org.apache.commons.io.file.PathUtils;
    027import org.apache.commons.io.filefilter.FileFilterUtils;
    028import org.apache.commons.io.filefilter.IOFileFilter;
    029import org.apache.commons.io.filefilter.TrueFileFilter;
    030
    031/**
    032 * Abstract class that walks through a directory hierarchy and provides subclasses with convenient hooks to add specific
    033 * behavior.
    034 * <p>
    035 * This class operates with a {@link FileFilter} and maximum depth to limit the files and directories visited. Commons
    036 * IO supplies many common filter implementations in the <a href="filefilter/package-summary.html"> filefilter</a>
    037 * package.
    038 * </p>
    039 * <p>
    040 * The following sections describe:
    041 * </p>
    042 * <ul>
    043 * <li><a href="#example">1. Example Implementation</a> - example {@code FileCleaner} implementation.</li>
    044 * <li><a href="#filter">2. Filter Example</a> - using {@link FileFilter}(s) with {@code DirectoryWalker}.</li>
    045 * <li><a href="#cancel">3. Cancellation</a> - how to implement cancellation behavior.</li>
    046 * </ul>
    047 *
    048 * <h2 id="example">1. Example Implementation</h2>
    049 *
    050 * There are many possible extensions, for example, to delete all files and '.svn' directories, and return a list of
    051 * deleted files:
    052 *
    053 * <pre>
    054 * public class FileCleaner extends DirectoryWalker {
    055 *
    056 *     public FileCleaner() {
    057 *         super();
    058 *     }
    059 *
    060 *     public List clean(File startDirectory) {
    061 *         List results = new ArrayList();
    062 *         walk(startDirectory, results);
    063 *         return results;
    064 *     }
    065 *
    066 *     protected boolean handleDirectory(File directory, int depth, Collection results) {
    067 *         // delete svn directories and then skip
    068 *         if (".svn".equals(directory.getName())) {
    069 *             directory.delete();
    070 *             return false;
    071 *         } else {
    072 *             return true;
    073 *         }
    074 *
    075 *     }
    076 *
    077 *     protected void handleFile(File file, int depth, Collection results) {
    078 *         // delete file and add to list of deleted
    079 *         file.delete();
    080 *         results.add(file);
    081 *     }
    082 * }
    083 * </pre>
    084 *
    085 * <h2 id="filter">2. Filter Example</h2>
    086 *
    087 * <p>
    088 * Choosing which directories and files to process can be a key aspect of using this class. This information can be
    089 * setup in three ways, via three different constructors.
    090 * </p>
    091 * <p>
    092 * The first option is to visit all directories and files. This is achieved via the no-args constructor.
    093 * </p>
    094 * <p>
    095 * The second constructor option is to supply a single {@link FileFilter} that describes the files and directories to
    096 * visit. Care must be taken with this option as the same filter is used for both directories and files.
    097 * </p>
    098 * <p>
    099 * For example, if you wanted all directories which are not hidden and files which end in ".txt":
    100 * </p>
    101 *
    102 * <pre>
    103 * public class FooDirectoryWalker extends DirectoryWalker {
    104 *     public FooDirectoryWalker(FileFilter filter) {
    105 *         super(filter, -1);
    106 *     }
    107 * }
    108 *
    109 * // Build up the filters and create the walker
    110 * // Create a filter for Non-hidden directories
    111 * IOFileFilter fooDirFilter = FileFilterUtils.andFileFilter(FileFilterUtils.directoryFileFilter,
    112 *     HiddenFileFilter.VISIBLE);
    113 *
    114 * // Create a filter for Files ending in ".txt"
    115 * IOFileFilter fooFileFilter = FileFilterUtils.andFileFilter(FileFilterUtils.fileFileFilter,
    116 *     FileFilterUtils.suffixFileFilter(".txt"));
    117 *
    118 * // Combine the directory and file filters using an OR condition
    119 * java.io.FileFilter fooFilter = FileFilterUtils.orFileFilter(fooDirFilter, fooFileFilter);
    120 *
    121 * // Use the filter to construct a DirectoryWalker implementation
    122 * FooDirectoryWalker walker = new FooDirectoryWalker(fooFilter);
    123 * </pre>
    124 * <p>
    125 * The third constructor option is to specify separate filters, one for directories and one for files. These are
    126 * combined internally to form the correct {@code FileFilter}, something which is very easy to get wrong when
    127 * attempted manually, particularly when trying to express constructs like 'any file in directories named docs'.
    128 * </p>
    129 * <p>
    130 * For example, if you wanted all directories which are not hidden and files which end in ".txt":
    131 * </p>
    132 *
    133 * <pre>
    134 *  public class FooDirectoryWalker extends DirectoryWalker {
    135 *    public FooDirectoryWalker(IOFileFilter dirFilter, IOFileFilter fileFilter) {
    136 *      super(dirFilter, fileFilter, -1);
    137 *    }
    138 *  }
    139 *
    140 *  // Use the filters to construct the walker
    141 *  FooDirectoryWalker walker = new FooDirectoryWalker(
    142 *    HiddenFileFilter.VISIBLE,
    143 *    FileFilterUtils.suffixFileFilter(".txt"),
    144 *  );
    145 * </pre>
    146 * <p>
    147 * This is much simpler than the previous example, and is why it is the preferred option for filtering.
    148 * </p>
    149 *
    150 * <h2 id="cancel">3. Cancellation</h2>
    151 *
    152 * <p>
    153 * The DirectoryWalker contains some of the logic required for cancel processing. Subclasses must complete the
    154 * implementation.
    155 * </p>
    156 * <p>
    157 * What {@code DirectoryWalker} does provide for cancellation is:
    158 * </p>
    159 * <ul>
    160 * <li>{@link CancelException} which can be thrown in any of the <i>lifecycle</i> methods to stop processing.</li>
    161 * <li>The {@code walk()} method traps thrown {@link CancelException} and calls the {@code handleCancelled()}
    162 * method, providing a place for custom cancel processing.</li>
    163 * </ul>
    164 * <p>
    165 * Implementations need to provide:
    166 * </p>
    167 * <ul>
    168 * <li>The decision logic on whether to cancel processing or not.</li>
    169 * <li>Constructing and throwing a {@link CancelException}.</li>
    170 * <li>Custom cancel processing in the {@code handleCancelled()} method.
    171 * </ul>
    172 * <p>
    173 * Two possible scenarios are envisaged for cancellation:
    174 * </p>
    175 * <ul>
    176 * <li><a href="#external">3.1 External / Multi-threaded</a> - cancellation being decided/initiated by an external
    177 * process.</li>
    178 * <li><a href="#internal">3.2 Internal</a> - cancellation being decided/initiated from within a DirectoryWalker
    179 * implementation.</li>
    180 * </ul>
    181 * <p>
    182 * The following sections provide example implementations for these two different scenarios.
    183 * </p>
    184 *
    185 * <h3 id="external">3.1 External / Multi-threaded</h3>
    186 *
    187 * <p>
    188 * This example provides a public {@code cancel()} method that can be called by another thread to stop the
    189 * processing. A typical example use-case would be a cancel button on a GUI. Calling this method sets a
    190 * <a href="http://java.sun.com/docs/books/jls/second_edition/html/classes.doc.html#36930"> volatile</a> flag to ensure
    191 * it will work properly in a multi-threaded environment. The flag is returned by the {@code handleIsCancelled()}
    192 * method, which will cause the walk to stop immediately. The {@code handleCancelled()} method will be the next,
    193 * and last, callback method received once cancellation has occurred.
    194 * </p>
    195 *
    196 * <pre>
    197 * public class FooDirectoryWalker extends DirectoryWalker {
    198 *
    199 *     private volatile boolean cancelled = false;
    200 *
    201 *     public void cancel() {
    202 *         cancelled = true;
    203 *     }
    204 *
    205 *     protected boolean handleIsCancelled(File file, int depth, Collection results) {
    206 *         return cancelled;
    207 *     }
    208 *
    209 *     protected void handleCancelled(File startDirectory, Collection results, CancelException cancel) {
    210 *         // implement processing required when a cancellation occurs
    211 *     }
    212 * }
    213 * </pre>
    214 *
    215 * <h3 id="internal">3.2 Internal</h3>
    216 *
    217 * <p>
    218 * This shows an example of how internal cancellation processing could be implemented. <b>Note</b> the decision logic
    219 * and throwing a {@link CancelException} could be implemented in any of the <i>lifecycle</i> methods.
    220 * </p>
    221 *
    222 * <pre>
    223 * public class BarDirectoryWalker extends DirectoryWalker {
    224 *
    225 *     protected boolean handleDirectory(File directory, int depth, Collection results) throws IOException {
    226 *         // cancel if hidden directory
    227 *         if (directory.isHidden()) {
    228 *             throw new CancelException(file, depth);
    229 *         }
    230 *         return true;
    231 *     }
    232 *
    233 *     protected void handleFile(File file, int depth, Collection results) throws IOException {
    234 *         // cancel if read-only file
    235 *         if (!file.canWrite()) {
    236 *             throw new CancelException(file, depth);
    237 *         }
    238 *         results.add(file);
    239 *     }
    240 *
    241 *     protected void handleCancelled(File startDirectory, Collection results, CancelException cancel) {
    242 *         // implement processing required when a cancellation occurs
    243 *     }
    244 * }
    245 * </pre>
    246 *
    247 * @param <T> The result type, like {@link File}.
    248 * @since 1.3
    249 * @deprecated Apache Commons IO no longer uses this class. Instead, use
    250 *             {@link PathUtils#walk(java.nio.file.Path, org.apache.commons.io.file.PathFilter, int, boolean, java.nio.file.FileVisitOption...)}
    251 *             or {@link Files#walkFileTree(java.nio.file.Path, java.util.Set, int, java.nio.file.FileVisitor)}, and
    252 *             friends.
    253 */
    254@Deprecated
    255public abstract class DirectoryWalker<T> {
    256
    257    /**
    258     * The file filter to use to filter files and directories.
    259     */
    260    private final FileFilter filter;
    261    /**
    262     * The limit on the directory depth to walk.
    263     */
    264    private final int depthLimit;
    265
    266    /**
    267     * Construct an instance with no filtering and unlimited <i>depth</i>.
    268     */
    269    protected DirectoryWalker() {
    270        this(null, -1);
    271    }
    272
    273    /**
    274     * Constructs an instance with a filter and limit the <i>depth</i> navigated to.
    275     * <p>
    276     * The filter controls which files and directories will be navigated to as
    277     * part of the walk. The {@link FileFilterUtils} class is useful for combining
    278     * various filters together. A {@code null} filter means that no
    279     * filtering should occur and all files and directories will be visited.
    280     * </p>
    281     *
    282     * @param filter  the filter to apply, null means visit all files
    283     * @param depthLimit  controls how <i>deep</i> the hierarchy is
    284     *  navigated to (less than 0 means unlimited)
    285     */
    286    protected DirectoryWalker(final FileFilter filter, final int depthLimit) {
    287        this.filter = filter;
    288        this.depthLimit = depthLimit;
    289    }
    290
    291    /**
    292     * Constructs an instance with a directory and a file filter and an optional
    293     * limit on the <i>depth</i> navigated to.
    294     * <p>
    295     * The filters control which files and directories will be navigated to as part
    296     * of the walk. This constructor uses {@link FileFilterUtils#makeDirectoryOnly(IOFileFilter)}
    297     * and {@link FileFilterUtils#makeFileOnly(IOFileFilter)} internally to combine the filters.
    298     * A {@code null} filter means that no filtering should occur.
    299     * </p>
    300     *
    301     * @param directoryFilter  the filter to apply to directories, null means visit all directories
    302     * @param fileFilter  the filter to apply to files, null means visit all files
    303     * @param depthLimit  controls how <i>deep</i> the hierarchy is
    304     *  navigated to (less than 0 means unlimited)
    305     */
    306    protected DirectoryWalker(IOFileFilter directoryFilter, IOFileFilter fileFilter, final int depthLimit) {
    307        if (directoryFilter == null && fileFilter == null) {
    308            this.filter = null;
    309        } else {
    310            directoryFilter = directoryFilter != null ? directoryFilter : TrueFileFilter.TRUE;
    311            fileFilter = fileFilter != null ? fileFilter : TrueFileFilter.TRUE;
    312            directoryFilter = FileFilterUtils.makeDirectoryOnly(directoryFilter);
    313            fileFilter = FileFilterUtils.makeFileOnly(fileFilter);
    314            this.filter = directoryFilter.or(fileFilter);
    315        }
    316        this.depthLimit = depthLimit;
    317    }
    318
    319    /**
    320     * Internal method that walks the directory hierarchy in a depth-first manner.
    321     * <p>
    322     * Users of this class do not need to call this method. This method will
    323     * be called automatically by another (public) method on the specific subclass.
    324     * </p>
    325     * <p>
    326     * Writers of subclasses should call this method to start the directory walk.
    327     * Once called, this method will emit events as it walks the hierarchy.
    328     * The event methods have the prefix {@code handle}.
    329     * </p>
    330     *
    331     * @param startDirectory  the directory to start from, not null
    332     * @param results  the collection of result objects, may be updated
    333     * @throws NullPointerException if the start directory is null
    334     * @throws IOException if an I/O Error occurs
    335     */
    336    protected final void walk(final File startDirectory, final Collection<T> results) throws IOException {
    337        Objects.requireNonNull(startDirectory, "startDirectory");
    338        try {
    339            handleStart(startDirectory, results);
    340            walk(startDirectory, 0, results);
    341            handleEnd(results);
    342        } catch(final CancelException cancel) {
    343            handleCancelled(startDirectory, results, cancel);
    344        }
    345    }
    346
    347    /**
    348     * Main recursive method to examine the directory hierarchy.
    349     *
    350     * @param directory  the directory to examine, not null
    351     * @param depth  the directory level (starting directory = 0)
    352     * @param results  the collection of result objects, may be updated
    353     * @throws IOException if an I/O Error occurs
    354     */
    355    private void walk(final File directory, final int depth, final Collection<T> results) throws IOException {
    356        checkIfCancelled(directory, depth, results);
    357        if (handleDirectory(directory, depth, results)) {
    358            handleDirectoryStart(directory, depth, results);
    359            final int childDepth = depth + 1;
    360            if (depthLimit < 0 || childDepth <= depthLimit) {
    361                checkIfCancelled(directory, depth, results);
    362                File[] childFiles = filter == null ? directory.listFiles() : directory.listFiles(filter);
    363                childFiles = filterDirectoryContents(directory, depth, childFiles);
    364                if (childFiles == null) {
    365                    handleRestricted(directory, childDepth, results);
    366                } else {
    367                    for (final File childFile : childFiles) {
    368                        if (childFile.isDirectory()) {
    369                            walk(childFile, childDepth, results);
    370                        } else {
    371                            checkIfCancelled(childFile, childDepth, results);
    372                            handleFile(childFile, childDepth, results);
    373                            checkIfCancelled(childFile, childDepth, results);
    374                        }
    375                    }
    376                }
    377            }
    378            handleDirectoryEnd(directory, depth, results);
    379        }
    380        checkIfCancelled(directory, depth, results);
    381    }
    382
    383    /**
    384     * Checks whether the walk has been cancelled by calling {@link #handleIsCancelled},
    385     * throwing a {@code CancelException} if it has.
    386     * <p>
    387     * Writers of subclasses should not normally call this method as it is called
    388     * automatically by the walk of the tree. However, sometimes a single method,
    389     * typically {@link #handleFile}, may take a long time to run. In that case,
    390     * you may wish to check for cancellation by calling this method.
    391     * </p>
    392     *
    393     * @param file  the current file being processed
    394     * @param depth  the current file level (starting directory = 0)
    395     * @param results  the collection of result objects, may be updated
    396     * @throws IOException if an I/O Error occurs
    397     */
    398    protected final void checkIfCancelled(final File file, final int depth, final Collection<T> results) throws
    399            IOException {
    400        if (handleIsCancelled(file, depth, results)) {
    401            throw new CancelException(file, depth);
    402        }
    403    }
    404
    405    /**
    406     * Overridable callback method invoked to determine if the entire walk
    407     * operation should be immediately cancelled.
    408     * <p>
    409     * This method should be implemented by those subclasses that want to
    410     * provide a public {@code cancel()} method available from another
    411     * thread. The design pattern for the subclass should be as follows:
    412     * </p>
    413     * <pre>
    414     *  public class FooDirectoryWalker extends DirectoryWalker {
    415     *    private volatile boolean cancelled = false;
    416     *
    417     *    public void cancel() {
    418     *        cancelled = true;
    419     *    }
    420     *    private void handleIsCancelled(File file, int depth, Collection results) {
    421     *        return cancelled;
    422     *    }
    423     *    protected void handleCancelled(File startDirectory,
    424     *              Collection results, CancelException cancel) {
    425     *        // implement processing required when a cancellation occurs
    426     *    }
    427     *  }
    428     * </pre>
    429     * <p>
    430     * If this method returns true, then the directory walk is immediately
    431     * cancelled. The next callback method will be {@link #handleCancelled}.
    432     * </p>
    433     * <p>
    434     * This implementation returns false.
    435     * </p>
    436     *
    437     * @param file  the file or directory being processed
    438     * @param depth  the current directory level (starting directory = 0)
    439     * @param results  the collection of result objects, may be updated
    440     * @return true if the walk has been cancelled
    441     * @throws IOException if an I/O Error occurs
    442     */
    443    @SuppressWarnings("unused") // Possibly thrown from subclasses.
    444    protected boolean handleIsCancelled(
    445            final File file, final int depth, final Collection<T> results) throws IOException {
    446        // do nothing - overridable by subclass
    447        return false;  // not cancelled
    448    }
    449
    450    /**
    451     * Overridable callback method invoked when the operation is cancelled.
    452     * The file being processed when the cancellation occurred can be
    453     * obtained from the exception.
    454     * <p>
    455     * This implementation just re-throws the {@link CancelException}.
    456     * </p>
    457     *
    458     * @param startDirectory  the directory that the walk started from
    459     * @param results  the collection of result objects, may be updated
    460     * @param cancel  the exception throw to cancel further processing
    461     * containing details at the point of cancellation.
    462     * @throws IOException if an I/O Error occurs
    463     */
    464    protected void handleCancelled(final File startDirectory, final Collection<T> results,
    465                       final CancelException cancel) throws IOException {
    466        // re-throw exception - overridable by subclass
    467        throw cancel;
    468    }
    469
    470    /**
    471     * Overridable callback method invoked at the start of processing.
    472     * <p>
    473     * This implementation does nothing.
    474     * </p>
    475     *
    476     * @param startDirectory  the directory to start from
    477     * @param results  the collection of result objects, may be updated
    478     * @throws IOException if an I/O Error occurs
    479     */
    480    @SuppressWarnings("unused") // Possibly thrown from subclasses.
    481    protected void handleStart(final File startDirectory, final Collection<T> results) throws IOException {
    482        // do nothing - overridable by subclass
    483    }
    484
    485    /**
    486     * Overridable callback method invoked to determine if a directory should be processed.
    487     * <p>
    488     * This method returns a boolean to indicate if the directory should be examined or not.
    489     * If you return false, the entire directory and any subdirectories will be skipped.
    490     * Note that this functionality is in addition to the filtering by file filter.
    491     * </p>
    492     * <p>
    493     * This implementation does nothing and returns true.
    494     * </p>
    495     *
    496     * @param directory  the current directory being processed
    497     * @param depth  the current directory level (starting directory = 0)
    498     * @param results  the collection of result objects, may be updated
    499     * @return true to process this directory, false to skip this directory
    500     * @throws IOException if an I/O Error occurs
    501     */
    502    @SuppressWarnings("unused") // Possibly thrown from subclasses.
    503    protected boolean handleDirectory(final File directory, final int depth, final Collection<T> results) throws
    504            IOException {
    505        // do nothing - overridable by subclass
    506        return true;  // process directory
    507    }
    508
    509    /**
    510     * Overridable callback method invoked at the start of processing each directory.
    511     * <p>
    512     * This implementation does nothing.
    513     * </p>
    514     *
    515     * @param directory  the current directory being processed
    516     * @param depth  the current directory level (starting directory = 0)
    517     * @param results  the collection of result objects, may be updated
    518     * @throws IOException if an I/O Error occurs
    519     */
    520    @SuppressWarnings("unused") // Possibly thrown from subclasses.
    521    protected void handleDirectoryStart(final File directory, final int depth, final Collection<T> results) throws
    522            IOException {
    523        // do nothing - overridable by subclass
    524    }
    525
    526    /**
    527     * Overridable callback method invoked with the contents of each directory.
    528     * <p>
    529     * This implementation returns the files unchanged
    530     * </p>
    531     *
    532     * @param directory  the current directory being processed
    533     * @param depth  the current directory level (starting directory = 0)
    534     * @param files the files (possibly filtered) in the directory, may be {@code null}
    535     * @return the filtered list of files
    536     * @throws IOException if an I/O Error occurs
    537     * @since 2.0
    538     */
    539    @SuppressWarnings("unused") // Possibly thrown from subclasses.
    540    protected File[] filterDirectoryContents(final File directory, final int depth, final File... files) throws
    541            IOException {
    542        return files;
    543    }
    544
    545    /**
    546     * Overridable callback method invoked for each (non-directory) file.
    547     * <p>
    548     * This implementation does nothing.
    549     * </p>
    550     *
    551     * @param file  the current file being processed
    552     * @param depth  the current directory level (starting directory = 0)
    553     * @param results  the collection of result objects, may be updated
    554     * @throws IOException if an I/O Error occurs
    555     */
    556    @SuppressWarnings("unused") // Possibly thrown from subclasses.
    557    protected void handleFile(final File file, final int depth, final Collection<T> results) throws IOException {
    558        // do nothing - overridable by subclass
    559    }
    560
    561    /**
    562     * Overridable callback method invoked for each restricted directory.
    563     * <p>
    564     * This implementation does nothing.
    565     * </p>
    566     *
    567     * @param directory  the restricted directory
    568     * @param depth  the current directory level (starting directory = 0)
    569     * @param results  the collection of result objects, may be updated
    570     * @throws IOException if an I/O Error occurs
    571     */
    572    @SuppressWarnings("unused") // Possibly thrown from subclasses.
    573    protected void handleRestricted(final File directory, final int depth, final Collection<T> results) throws
    574            IOException {
    575        // do nothing - overridable by subclass
    576    }
    577
    578    /**
    579     * Overridable callback method invoked at the end of processing each directory.
    580     * <p>
    581     * This implementation does nothing.
    582     * </p>
    583     *
    584     * @param directory  the directory being processed
    585     * @param depth  the current directory level (starting directory = 0)
    586     * @param results  the collection of result objects, may be updated
    587     * @throws IOException if an I/O Error occurs
    588     */
    589    @SuppressWarnings("unused") // Possibly thrown from subclasses.
    590    protected void handleDirectoryEnd(final File directory, final int depth, final Collection<T> results) throws
    591            IOException {
    592        // do nothing - overridable by subclass
    593    }
    594
    595    /**
    596     * Overridable callback method invoked at the end of processing.
    597     * <p>
    598     * This implementation does nothing.
    599     * </p>
    600     *
    601     * @param results  the collection of result objects, may be updated
    602     * @throws IOException if an I/O Error occurs
    603     */
    604    @SuppressWarnings("unused") // Possibly thrown from subclasses.
    605    protected void handleEnd(final Collection<T> results) throws IOException {
    606        // do nothing - overridable by subclass
    607    }
    608
    609    /**
    610     * CancelException is thrown in DirectoryWalker to cancel the current
    611     * processing.
    612     */
    613    public static class CancelException extends IOException {
    614
    615        /** Serialization id. */
    616        private static final long serialVersionUID = 1347339620135041008L;
    617
    618        /** The file being processed when the exception was thrown. */
    619        private final File file;
    620        /** The file depth when the exception was thrown. */
    621        private final int depth;
    622
    623        /**
    624         * Constructs a {@code CancelException} with
    625         * the file and depth when cancellation occurred.
    626         *
    627         * @param file  the file when the operation was cancelled, may be null
    628         * @param depth  the depth when the operation was cancelled, may be null
    629         */
    630        public CancelException(final File file, final int depth) {
    631            this("Operation Cancelled", file, depth);
    632        }
    633
    634        /**
    635         * Constructs a {@code CancelException} with
    636         * an appropriate message and the file and depth when
    637         * cancellation occurred.
    638         *
    639         * @param message  the detail message
    640         * @param file  the file when the operation was cancelled
    641         * @param depth  the depth when the operation was cancelled
    642         */
    643        public CancelException(final String message, final File file, final int depth) {
    644            super(message);
    645            this.file = file;
    646            this.depth = depth;
    647        }
    648
    649        /**
    650         * Returns the file when the operation was cancelled.
    651         *
    652         * @return the file when the operation was cancelled
    653         */
    654        public File getFile() {
    655            return file;
    656        }
    657
    658        /**
    659         * Returns the depth when the operation was cancelled.
    660         *
    661         * @return the depth when the operation was cancelled
    662         */
    663        public int getDepth() {
    664            return depth;
    665        }
    666    }
    667}