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.List;
  
  import org.apache.commons.io.IOCase;
  
  /**
   * Filters filenames for a certain prefix.
   * <p>
   * For example, to print all files and directories in the 
   * current directory whose name starts with <code>Test</code>:
   *
   * <pre>
   * File dir = new File(".");
   * String[] files = dir.list( new PrefixFileFilter("Test") );
   * 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 Federico Barbieri
   * @author Serge Knystautas
   * @author Peter Donald
   * @see FileFilterUtils#prefixFileFilter(String)
   * @see FileFilterUtils#prefixFileFilter(String, IOCase)
   */
  public class PrefixFileFilter extends AbstractFileFilter implements Serializable {
      
      /** The filename prefixes to search for */
      private final String[] prefixes;
  
      /** Whether the comparison is case sensitive. */
      private final IOCase caseSensitivity;
  
      /**
       * Constructs a new Prefix file filter for a single prefix.
       * 
       * @param prefix  the prefix to allow, must not be null
       * @throws IllegalArgumentException if the prefix is null
       */
      public PrefixFileFilter(String prefix) {
          this(prefix, IOCase.SENSITIVE);
      }
  
      /**
       * Constructs a new Prefix file filter for a single prefix 
       * specifying case-sensitivity.
       * 
       * @param prefix  the prefix to allow, must not be null
       * @param caseSensitivity  how to handle case sensitivity, null means case-sensitive
       * @throws IllegalArgumentException if the prefix is null
       * @since Commons IO 1.4
       */
      public PrefixFileFilter(String prefix, IOCase caseSensitivity) {
          if (prefix == null) {
              throw new IllegalArgumentException("The prefix must not be null");
          }
          this.prefixes = new String[] {prefix};
          this.caseSensitivity = (caseSensitivity == null ? IOCase.SENSITIVE : caseSensitivity);
      }
  
      /**
       * Constructs a new Prefix file filter for any of an array of prefixes.
       * <p>
       * The array is not cloned, so could be changed after constructing the
       * instance. This would be inadvisable however.
       * 
       * @param prefixes  the prefixes to allow, must not be null
       * @throws IllegalArgumentException if the prefix array is null
       */
      public PrefixFileFilter(String[] prefixes) {
          this(prefixes, IOCase.SENSITIVE);
      }
  
      /**
       * Constructs a new Prefix file filter for any of an array of prefixes
       * specifying case-sensitivity.
       * <p>
       * The array is not cloned, so could be changed after constructing the
       * instance. This would be inadvisable however.
       * 
       * @param prefixes  the prefixes to allow, must not be null
       * @param caseSensitivity  how to handle case sensitivity, null means case-sensitive
       * @throws IllegalArgumentException if the prefix is null
       * @since Commons IO 1.4
       */
      public PrefixFileFilter(String[] prefixes, IOCase caseSensitivity) {
          if (prefixes == null) {
              throw new IllegalArgumentException("The array of prefixes must not be null");
          }
          this.prefixes = new String[prefixes.length];
          System.arraycopy(prefixes, 0, this.prefixes, 0, prefixes.length);
          this.caseSensitivity = (caseSensitivity == null ? IOCase.SENSITIVE : caseSensitivity);
      }
  
      /**
       * Constructs a new Prefix file filter for a list of prefixes.
       * 
       * @param prefixes  the prefixes to allow, must not be null
       * @throws IllegalArgumentException if the prefix list is null
       * @throws ClassCastException if the list does not contain Strings
       */
      public PrefixFileFilter(List<String> prefixes) {
          this(prefixes, IOCase.SENSITIVE);
      }
  
      /**
       * Constructs a new Prefix file filter for a list of prefixes
       * specifying case-sensitivity.
       * 
       * @param prefixes  the prefixes to allow, must not be null
       * @param caseSensitivity  how to handle case sensitivity, null means case-sensitive
       * @throws IllegalArgumentException if the prefix list is null
       * @throws ClassCastException if the list does not contain Strings
       * @since Commons IO 1.4
       */
      public PrefixFileFilter(List<String> prefixes, IOCase caseSensitivity) {
          if (prefixes == null) {
              throw new IllegalArgumentException("The list of prefixes must not be null");
          }
          this.prefixes = prefixes.toArray(new String[prefixes.size()]);
          this.caseSensitivity = (caseSensitivity == null ? IOCase.SENSITIVE : caseSensitivity);
      }
  
      /**
       * Checks to see if the filename starts with the prefix.
       * 
       * @param file  the File to check
       * @return true if the filename starts with one of our prefixes
       */
      @Override
      public boolean accept(File file) {
          String name = file.getName();
          for (String prefix : this.prefixes) {
              if (caseSensitivity.checkStartsWith(name, prefix)) {
                  return true;
              }
          }
          return false;
      }
      
      /**
       * Checks to see if the filename starts with the prefix.
       * 
       * @param file  the File directory
       * @param name  the filename
       * @return true if the filename starts with one of our prefixes
       */
      @Override
      public boolean accept(File file, String name) {
          for (String prefix : prefixes) {
              if (caseSensitivity.checkStartsWith(name, prefix)) {
                  return true;
              }
          }
          return false;
      }
  
      /**
       * Provide a String representaion of this file filter.
       *
       * @return a String representaion
       */
      @Override
      public String toString() {
          StringBuilder buffer = new StringBuilder();
          buffer.append(super.toString());
          buffer.append("(");
          if (prefixes != null) {
              for (int i = 0; i < prefixes.length; i++) {
                  if (i > 0) {
                      buffer.append(",");
                  }
                  buffer.append(prefixes[i]);
              }
          }
          buffer.append(")");
          return buffer.toString();
      }
      
  }
  