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 files or directories that are empty.
   * <p>
   * If the <code>File</code> is a directory it checks that
   * it contains no files.
   * <p>
   * Example, showing how to print out a list of the 
   * current directory's empty files/directories:
   *
   * <pre>
   * File dir = new File(".");
   * String[] files = dir.list( EmptyFileFilter.EMPTY );
   * for ( int i = 0; i &lt; files.length; i++ ) {
   *     System.out.println(files[i]);
   * }
   * </pre>
   *
   * <p>
   * Example, showing how to print out a list of the 
   * current directory's non-empty files/directories:
   *
   * <pre>
   * File dir = new File(".");
   * String[] files = dir.list( EmptyFileFilter.NOT_EMPTY );
   * for ( int i = 0; i &lt; files.length; i++ ) {
   *     System.out.println(files[i]);
   * }
   * </pre>
   *
   * @since Commons IO 1.3
   * @version $Revision: 659817 $
   */
  public class EmptyFileFilter extends AbstractFileFilter implements Serializable {
      
      /** Singleton instance of <i>empty</i> filter */
      public static final IOFileFilter EMPTY = new EmptyFileFilter();
      
      /** Singleton instance of <i>not-empty</i> filter */
      public static final IOFileFilter NOT_EMPTY = new NotFileFilter(EMPTY);
      
      /**
       * Restrictive consructor.
       */
      protected EmptyFileFilter() {
      }
      
      /**
       * Checks to see if the file is empty.
       * 
       * @param file  the file or directory to check
       * @return <code>true</code> if the file or directory
       *  is <i>empty</i>, otherwise <code>false</code>.
       */
      @Override
      public boolean accept(File file) {
          if (file.isDirectory()) {
              File[] files = file.listFiles();
              return (files == null || files.length == 0);
          } else {
              return (file.length() == 0);
          }
      }
      
  }
  