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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.apache.commons.vfs2.filter;
18  
19  import java.io.Serializable;
20  
21  import org.apache.commons.vfs2.FileContent;
22  import org.apache.commons.vfs2.FileFilter;
23  import org.apache.commons.vfs2.FileObject;
24  import org.apache.commons.vfs2.FileSelectInfo;
25  import org.apache.commons.vfs2.FileSystemException;
26  import org.apache.commons.vfs2.FileType;
27  
28  /**
29   * This filter accepts files or directories that are empty.
30   * <p>
31   * If the <code>File</code> is a directory it checks that it contains no files.
32   * </p>
33   * <p>
34   * Example, showing how to print out a list of the current directory's empty files/directories:
35   * </p>
36   *
37   * <pre>
38   * FileSystemManager fsManager = VFS.getManager();
39   * FileObject dir = fsManager.toFileObject(new File(&quot;.&quot;));
40   * FileObject[] files = dir.findFiles(new FileFilterSelector(EmptyFileFilter.EMPTY));
41   * for (int i = 0; i &lt; files.length; i++) {
42   *     System.out.println(files[i]);
43   * }
44   * </pre>
45   *
46   * <p>
47   * Example, showing how to print out a list of the current directory's non-empty files/directories:
48   * </p>
49   *
50   * <pre>
51   * FileSystemManager fsManager = VFS.getManager();
52   * FileObject dir = fsManager.toFileObject(new File(&quot;.&quot;));
53   * FileObject[] files = dir.findFiles(new FileFilterSelector(EmptyFileFilter.NOT_EMPTY));
54   * for (int i = 0; i &lt; files.length; i++) {
55   *     System.out.println(files[i]);
56   * }
57   * </pre>
58   *
59   * @author This code was originally ported from Apache Commons IO File Filter
60   * @see "http://commons.apache.org/proper/commons-io/"
61   * @since 2.4
62   */
63  public class EmptyFileFilter implements FileFilter, Serializable {
64  
65      private static final long serialVersionUID = 1L;
66  
67      /** Singleton instance of <i>empty</i> filter. */
68      public static final FileFilter EMPTY = new EmptyFileFilter();
69  
70      /** Singleton instance of <i>not-empty</i> filter. */
71      public static final FileFilter NOT_EMPTY = new NotFileFilter(EMPTY);
72  
73      /**
74       * Restrictive constructor.
75       */
76      protected EmptyFileFilter() {
77      }
78  
79      /**
80       * Checks to see if the file is empty. A non-existing file is also considered empty.
81       *
82       * @param fileInfo the file or directory to check
83       *
84       * @return {@code true} if the file or directory is <i>empty</i>, otherwise {@code false}.
85       * @throws FileSystemException Thrown for file system errors.
86       */
87      @Override
88      public boolean accept(final FileSelectInfo fileInfo) throws FileSystemException {
89          try (final FileObject file = fileInfo.getFile()) {
90              if (!file.exists()) {
91                  return true;
92              }
93              if (file.getType() == FileType.FOLDER) {
94                  final FileObject[] files = file.getChildren();
95                  return files == null || files.length == 0;
96              }
97              try (final FileContent content = file.getContent();) {
98                  return content.getSize() == 0;
99              }
100         }
101     }
102 
103 }