code: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   * 
   *      http://www.apache.org/licenses/LICENSE-2.0
   * 
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.commons.io.filefilter;
  
  import java.io.File;
  import java.io.Serializable;
  
  /**
   * This filter accepts <code>File</code>s that are directories.
   * <p>
   * For example, here is how to print out a list of the 
   * current directory's subdirectories:
   *
   * <pre>
   * File dir = new File(".");
   * String[] files = dir.list( DirectoryFileFilter.INSTANCE );
   * for ( int i = 0; i &lt; files.length; i++ ) {
   *     System.out.println(files[i]);
   * }
   * </pre>
   *
   * @since Commons IO 1.0
   * @version $Revision: 1005099 $ $Date: 2010-10-06 17:13:01 +0100 (Wed, 06 Oct 2010) $
   *
   * @author Stephen Colebourne
   * @author Peter Donald
   * @see FileFilterUtils#directoryFileFilter()
   */
  public class DirectoryFileFilter extends AbstractFileFilter implements Serializable {
  
      /**
       * Singleton instance of directory filter.
       * @since Commons IO 1.3
       */
      public static final IOFileFilter DIRECTORY = new DirectoryFileFilter();
      /**
       * Singleton instance of directory filter.
       * Please use the identical DirectoryFileFilter.DIRECTORY constant.
       * The new name is more JDK 1.5 friendly as it doesn't clash with other
       * values when using static imports.
       */
      public static final IOFileFilter INSTANCE = DIRECTORY;
  
      /**
       * Restrictive consructor.
       */
      protected DirectoryFileFilter() {
      }
  
      /**
       * Checks to see if the file is a directory.
       *
       * @param file  the File to check
       * @return true if the file is a directory
       */
      @Override
      public boolean accept(File file) {
          return file.isDirectory();
      }
  
  }
  