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;
  import java.util.regex.Pattern;
  
  import org.apache.commons.io.IOCase;
  
  /**
   * Filters files using supplied regular expression(s).
   * <p/>
   * See java.util.regex.Pattern for regex matching rules
   * <p/>
   *
   * <p/>
   * e.g.
   * <pre>
   * File dir = new File(".");
   * FileFilter fileFilter = new RegexFileFilter("^.*[tT]est(-\\d+)?\\.java$");
   * File[] files = dir.listFiles(fileFilter);
   * for (int i = 0; i < files.length; i++) {
   *   System.out.println(files[i]);
   * }
   * </pre>
   *
   * @author Oliver Siegmar
   * @version $Revision: 1.1.2.1.2.1 $
   * @since Commons IO 1.4
   */
  public class RegexFileFilter extends AbstractFileFilter implements Serializable {
  
      /** The regular expression pattern that will be used to match filenames */
      private final Pattern pattern;
  
      /**
       * Construct a new regular expression filter.
       *
       * @param pattern regular string expression to match
       * @throws IllegalArgumentException if the pattern is null
       */
      public RegexFileFilter(String pattern) {
          if (pattern == null) {
              throw new IllegalArgumentException("Pattern is missing");
          }
  
          this.pattern = Pattern.compile(pattern);
      }
  
      /**
       * Construct a new regular expression filter with the specified flags case sensitivity.
       *
       * @param pattern regular string expression to match
       * @param caseSensitivity  how to handle case sensitivity, null means case-sensitive
       * @throws IllegalArgumentException if the pattern is null
       */
      public RegexFileFilter(String pattern, IOCase caseSensitivity) {
          if (pattern == null) {
              throw new IllegalArgumentException("Pattern is missing");
          }
          int flags = 0;
          if (caseSensitivity != null && !caseSensitivity.isCaseSensitive()) {
              flags = Pattern.CASE_INSENSITIVE;
          }
          this.pattern = Pattern.compile(pattern, flags);
      }
  
      /**
       * Construct a new regular expression filter with the specified flags.
       *
       * @param pattern regular string expression to match
       * @param flags pattern flags - e.g. {@link Pattern#CASE_INSENSITIVE}
       * @throws IllegalArgumentException if the pattern is null
       */
      public RegexFileFilter(String pattern, int flags) {
          if (pattern == null) {
              throw new IllegalArgumentException("Pattern is missing");
          }
          this.pattern = Pattern.compile(pattern, flags);
      }
  
      /**
       * Construct a new regular expression filter for a compiled regular expression
       *
       * @param pattern regular expression to match
       * @throws IllegalArgumentException if the pattern is null
       */
      public RegexFileFilter(Pattern pattern) {
          if (pattern == null) {
              throw new IllegalArgumentException("Pattern is missing");
          }
  
          this.pattern = pattern;
      }
  
      /**
       * Checks to see if the filename matches one of the regular expressions.
       *
       * @param dir   the file directory
       * @param name  the filename
       * @return true if the filename matches one of the regular expressions
       */
      @Override
      public boolean accept(File dir, String name) {
          return (pattern.matcher(name).matches());
      }
  
  }
  