1   /*
2    * Copyright (C) 2006 The Guava Authors
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    * http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  
17  package com.google.common.io;
18  
19  import com.google.common.annotations.Beta;
20  import com.google.common.base.Preconditions;
21  
22  import java.io.File;
23  import java.io.FilenameFilter;
24  import java.util.regex.Pattern;
25  import java.util.regex.PatternSyntaxException;
26  
27  import javax.annotation.Nullable;
28  
29  /**
30   * File name filter that only accepts files matching a regular expression. This
31   * class is thread-safe and immutable.
32   *
33   * @author Apple Chow
34   * @since 1.0
35   */
36  @Beta
37  public final class PatternFilenameFilter implements FilenameFilter {
38  
39    private final Pattern pattern;
40  
41    /**
42     * Constructs a pattern file name filter object.
43     * @param patternStr the pattern string on which to filter file names
44     *
45     * @throws PatternSyntaxException if pattern compilation fails (runtime)
46     */
47    public PatternFilenameFilter(String patternStr) {
48      this(Pattern.compile(patternStr));
49    }
50  
51    /**
52     * Constructs a pattern file name filter object.
53     * @param pattern the pattern on which to filter file names
54     */
55    public PatternFilenameFilter(Pattern pattern) {
56      this.pattern = Preconditions.checkNotNull(pattern);
57    }
58  
59    @Override public boolean accept(@Nullable File dir, String fileName) {
60      return pattern.matcher(fileName).matches();
61    }
62  }