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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.io.filefilter;
     18 
     19 import java.io.File;
     20 import java.io.Serializable;
     21 
     22 /**
     23  * This filter accepts <code>File</code>s that can be read.
     24  * <p>
     25  * Example, showing how to print out a list of the
     26  * current directory's <i>readable</i> files:
     27  *
     28  * <pre>
     29  * File dir = new File(".");
     30  * String[] files = dir.list( CanReadFileFilter.CAN_READ );
     31  * for ( int i = 0; i &lt; files.length; i++ ) {
     32  *     System.out.println(files[i]);
     33  * }
     34  * </pre>
     35  *
     36  * <p>
     37  * Example, showing how to print out a list of the
     38  * current directory's <i>un-readable</i> files:
     39  *
     40  * <pre>
     41  * File dir = new File(".");
     42  * String[] files = dir.list( CanReadFileFilter.CANNOT_READ );
     43  * for ( int i = 0; i &lt; files.length; i++ ) {
     44  *     System.out.println(files[i]);
     45  * }
     46  * </pre>
     47  *
     48  * <p>
     49  * Example, showing how to print out a list of the
     50  * current directory's <i>read-only</i> files:
     51  *
     52  * <pre>
     53  * File dir = new File(".");
     54  * String[] files = dir.list( CanReadFileFilter.READ_ONLY );
     55  * for ( int i = 0; i &lt; files.length; i++ ) {
     56  *     System.out.println(files[i]);
     57  * }
     58  * </pre>
     59  *
     60  * @since Commons IO 1.3
     61  * @version $Revision: 587916 $
     62  */
     63 public class CanReadFileFilter extends AbstractFileFilter implements Serializable {
     64 
     65     /** Singleton instance of <i>readable</i> filter */
     66     public static final IOFileFilter CAN_READ = new CanReadFileFilter();
     67 
     68     /** Singleton instance of not <i>readable</i> filter */
     69     public static final IOFileFilter CANNOT_READ = new NotFileFilter(CAN_READ);
     70 
     71     /** Singleton instance of <i>read-only</i> filter */
     72     public static final IOFileFilter READ_ONLY = new AndFileFilter(CAN_READ,
     73                                                 CanWriteFileFilter.CANNOT_WRITE);
     74 
     75     /**
     76      * Restrictive consructor.
     77      */
     78     protected CanReadFileFilter() {
     79     }
     80 
     81     /**
     82      * Checks to see if the file can be read.
     83      *
     84      * @param file  the File to check.
     85      * @return <code>true</code> if the file can be
     86      *  read, otherwise <code>false</code>.
     87      */
     88     public boolean accept(File file) {
     89         return file.canRead();
     90     }
     91 
     92 }
     93