Java Tutorial/File/FileFilter

A suffix based file filter.

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 * JBoss, Home of Professional Open Source
 * Copyright 2005, JBoss Inc., and individual contributors as indicated
 * by the @authors tag. See the copyright.txt in the distribution for a
 * full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
import java.io.File;
import java.io.FileFilter;
/**
 * A <em>suffix</em> based file filter.
 * 
 * @version <tt>$Revision: 1958 $</tt>
 * @author 
 */
public class FileSuffixFilter implements FileFilter {
  /** A list of suffixes which files must have to be accepted. */
  protected final String suffixes[];
  /** Flag to signal that we want to ignore the case. */
  protected final boolean ignoreCase;
  /**
   * Construct a <tt>FileSuffixFilter</tt>.
   * 
   * @param suffixes
   *          A list of suffixes which files mut have to be accepted.
   * @param ignoreCase
   *          <tt>True</tt> if the filter should be case-insensitive.
   */
  public FileSuffixFilter(final String suffixes[], final boolean ignoreCase) {
    this.ignoreCase = ignoreCase;
    if (ignoreCase) {
      this.suffixes = new String[suffixes.length];
      for (int i = 0; i < suffixes.length; i++) {
        this.suffixes[i] = suffixes[i].toLowerCase();
      }
    } else {
      this.suffixes = suffixes;
    }
  }
  /**
   * Construct a <tt>FileSuffixFilter</tt>.
   * 
   * @param suffixes
   *          A list of suffixes which files mut have to be accepted.
   */
  public FileSuffixFilter(final String suffixes[]) {
    this(suffixes, false);
  }
  /**
   * Construct a <tt>FileSuffixFilter</tt>.
   * 
   * @param suffix
   *          The suffix which files must have to be accepted.
   * @param ignoreCase
   *          <tt>True</tt> if the filter should be case-insensitive.
   */
  public FileSuffixFilter(final String suffix, final boolean ignoreCase) {
    this(new String[] { suffix }, ignoreCase);
  }
  /**
   * Construct a case sensitive <tt>FileSuffixFilter</tt>.
   * 
   * @param suffix
   *          The suffix which files must have to be accepted.
   */
  public FileSuffixFilter(final String suffix) {
    this(suffix, false);
  }
  /**
   * Check if a file is acceptible.
   * 
   * @param file
   *          The file to check.
   * @return <tt>true</tt> if the file is acceptable.
   */
  public boolean accept(final File file) {
    boolean success = false;
    for (int i = 0; i < suffixes.length && !success; i++) {
      if (ignoreCase)
        success = file.getName().toLowerCase().endsWith(suffixes[i]);
      else
        success = file.getName().endsWith(suffixes[i]);
    }
    return success;
  }
}

Create custom File filter

import java.io.File;
import java.io.FileFilter;
public class MainClass {
  public static void main(String[] args) {
    File cwd = new File(System.getProperty("user.dir"));
    File[] htmlFiles = cwd.listFiles(new HTMLFileFilter());
    for (int i = 0; i < htmlFiles.length; i++) {
      System.out.println(htmlFiles[i]);
    }
  }
}
class HTMLFileFilter implements FileFilter {
  public boolean accept(File pathname) {
    if (pathname.getName().endsWith(".html"))
      return true;
    if (pathname.getName().endsWith(".htm"))
      return true;
    return false;
  }
}

Custom File Filter

import java.io.File;
import java.util.Enumeration;
import java.util.Hashtable;
import javax.swing.filechooser.FileFilter;
public class CustomFileFilter extends FileFilter {
  private Hashtable filters = null;
  private String description = null;
  private String fullDescription = null;
  private boolean useExtensionsInDescription = true;
  public CustomFileFilter() {
    this.filters = new Hashtable();
  }
  public CustomFileFilter(String extension) {
    this(extension, null);
  }
  public CustomFileFilter(String extension, String description) {
    this();
    if (extension != null)
      addExtension(extension);
    if (description != null)
      setDescription(description);
  }
  public CustomFileFilter(String[] filters) {
    this(filters, null);
  }
  public CustomFileFilter(String[] filters, String description) {
    this();
    for (int i = 0; i < filters.length; i++) {
      addExtension(filters[i]);
    }
    if (description != null)
      setDescription(description);
  }
  public boolean accept(File f) {
    if (f != null) {
      if (f.isDirectory()) {
        return true;
      }
      String extension = getExtension(f);
      if (extension != null && filters.get(getExtension(f)) != null) {
        return true;
      }
    }
    return false;
  }
  public String getExtension(File f) {
    if (f != null) {
      String filename = f.getName();
      int i = filename.lastIndexOf(".");
      if (i > 0 && i < filename.length() - 1) {
        return filename.substring(i + 1).toLowerCase();
      }
    }
    return null;
  }
  public void addExtension(String extension) {
    if (filters == null) {
      filters = new Hashtable(5);
    }
    filters.put(extension.toLowerCase(), this);
    fullDescription = null;
  }
  public String getDescription() {
    if (fullDescription == null) {
      if (description == null || isExtensionListInDescription()) {
        fullDescription = description == null ? "(" : description + " (";
        Enumeration extensions = filters.keys();
        if (extensions != null) {
          fullDescription += "." + (String) extensions.nextElement();
          while (extensions.hasMoreElements()) {
            fullDescription += ", " + (String) extensions.nextElement();
          }
        }
        fullDescription += ")";
      } else {
        fullDescription = description;
      }
    }
    return fullDescription;
  }
  public void setDescription(String description) {
    this.description = description;
    fullDescription = null;
  }
  public void setExtensionListInDescription(boolean b) {
    useExtensionsInDescription = b;
    fullDescription = null;
  }
  public boolean isExtensionListInDescription() {
    return useExtensionsInDescription;
  }
}

Files filter that filters files by their suffix (or extension)

/*
 * $Id: SuffixFilenameFilter.java,v 1.1.1.1 2005/04/07 18:36:22 pocho Exp $
 */
import java.io.File;
import java.io.FilenameFilter;
import javax.swing.filechooser.FileFilter;
/**
 * Files filter that filters files by their suffix (or extension).
 * It can be used as file filter for {@link javax.swing.JFileChooser} or
 * as file filter for io operations (@link java.io.File#listFiles(java.io.FilenameFilter)}.
 * 
 * @version $Name:  $ - $Revision: 1.1.1.1 $ - $Date: 2005/04/07 18:36:22 $
 * TODO Test
 */
public class SuffixFilenameFilter extends FileFilter implements FilenameFilter {
  
  /** Suffix of files */
  private String suffix;
  
  /** Description of suffix (i.e. .jpg may have description JPG)*/
  private String description;
  
  /** Full description of filter - (i.e. JPG (.jpg) */
  private String fullDescription;
  
  /** Indicates whether to use suffix in brackets after description */
  private boolean useExtensionInDescription = true;
  /**
   * Creates new instance with a given accepted suffix of file names.
   *
   * @param suffix used suffix of files (i.e. extension ".xml")
   */
  public SuffixFilenameFilter(String suffix) {
    this(suffix, null);
  }
  /**
   * Creates new instance with a given accepted suffix of file names.
   *
   * @param suffix used suffix of files (i.e. extension ".xml")
   */
  public SuffixFilenameFilter(String suffix, String description) {
    super();
    setSuffix(suffix);
    setDescription(description);
  }
  /**
   * Indicates whether the name is accepted by this filter or not.
   * File must ending with given mask of this filter.
   *
   * @param dir File
   * @param name String
   * @return boolean
   */
  public boolean accept(File dir, String name){
  if (name.lastIndexOf(suffix) > 0)
      return true;
    else
      return false;
  }
  public boolean accept(File file) {
    if (file != null) {
      if (file.isDirectory() || accept(file.getParentFile(), file.getName()))
          return true;
    }
    return false;
  }
  /**
   * Returns description of this filter - if {@link #isExtensionInDescription()}
   * is <code>true</code> then it creates description in following shape:<br>
   * <code>description (suffix)</code>. Otherwise it only returns description.
   * 
   * @see javax.swing.filechooser.FileFilter#getDescription()
   */
  public String getDescription() {
    if (fullDescription == null && isExtensionInDescription()) {
        fullDescription = description==null ? "(" : description + " (";
        fullDescription += suffix + ")";
    }
    return fullDescription;
  }
  /**
   * Sets whether to use suffix in description of this filter.
   * 
   * @param b
   */
  public void setExtensionInDescription(boolean b) {
    useExtensionInDescription = b;
    fullDescription = null;
  }
  public boolean isExtensionInDescription() {
    return useExtensionInDescription;
  }
  public void setSuffix(String suffix) {
    this.suffix = suffix;
    fullDescription = null;
  }
  public void setDescription(String description) {
    this.description = description;
    fullDescription = null;
  }
  
  public String getExtension() {
    return suffix;
  }
  
  public String getSimpleDescription() {
    return description;
  }
}

Filter by file

import java.io.File;
import java.io.FileFilter;
import java.io.FilenameFilter;
public class Main {
  public static void main(String[] argv) throws Exception {
    File dir = new File("c:\\temp");
    FileFilter fileFilter = new FileFilter() {
      public boolean accept(File file) {
        return file.isDirectory();
      }
    };
    File[] files = dir.listFiles(fileFilter);
    
  }
}

Filters files based on the extension (what the filename ends with)

/****************************************************************
 * 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.                                           *
 ****************************************************************/
import java.io.File;
import java.io.FilenameFilter;
/**
 * This filters files based on the extension (what the filename
 * ends with). This is used in retrieving all the files of a
 * particular type.
 *
 * Eg., to retrieve and print all <code>*.java</code> files in the current directory:
 *
 * <pre>
 * File dir = new File(".");
 * String[] files = dir.list( new ExtensionFileFilter( new String[]{"java"} ) );
 * for (int i=0; i&lt;files.length; i++)
 * {
 *     System.out.println(files[i]);
 * }
 * </pre>
 *
 * @author  Federico Barbieri <fede@apache.org>
 * @author Serge Knystautas <sergek@lokitech.ru>
 * @author Peter Donald
 * @version CVS $Revision: 494012 $ $Date: 2007-01-08 11:23:58 +0100 (Mo, 08 Jan 2007) $
 * @since 4.0
 */
public class ExtensionFileFilter
    implements FilenameFilter
{
    private String[] m_extensions;
    public ExtensionFileFilter( final String[] extensions )
    {
        m_extensions = extensions;
    }
    public ExtensionFileFilter( final String extension )
    {
        m_extensions = new String[]{extension};
    }
    public boolean accept( final File file, final String name )
    {
        for( int i = 0; i < m_extensions.length; i++ )
        {
            if( name.endsWith( m_extensions[ i ] ) )
            {
                return true;
            }
        }
        return false;
    }
}

Generic File Filter

import java.io.File;
import javax.swing.filechooser.FileFilter;
public class GenericFileFilter extends FileFilter {
  private String[] fileExts;
  private String description;
  private String extension;
  public GenericFileFilter(String[] filesExtsIn, String description) {
    fileExts = filesExtsIn;
    this.description = description;
  }
  public boolean accept(File f) {
    if (f.isDirectory()) {
      return true;
    }
    extension = getExtension(f);
    if (extension != null) {
      for (int i = 0; i < fileExts.length; i++) {
        if (check(fileExts[i]))
          return true;
      }
    }
    return false;
  }
  private boolean check(String in) {
    return extension.equalsIgnoreCase(in);
  }
  public String getDescription() {
    return description;
  }
  private String getExtension(File file) {
    String filename = file.getName();
    int length = filename.length();
    int i = filename.lastIndexOf(".");
    if (i > 0 && i < length - 1)
      return filename.substring(i + 1).toLowerCase();
    return null;
  }
}

Inverted File Filter

/****************************************************************
 * 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.                                           *
 ****************************************************************/

import java.io.File;
import java.io.FilenameFilter;
/**
 * This takes a <code>FilenameFilter<code> as input and inverts the selection.
 * This is used in retrieving files that are not accepted by a filter.
 *
 * @author 
 * @version CVS $Revision: 494012 $ $Date: 2007-01-08 11:23:58 +0100 (Mo, 08 Jan 2007) $
 * @since 4.0
 */
public class InvertedFileFilter
    implements FilenameFilter
{
    private final FilenameFilter m_originalFilter;
    public InvertedFileFilter( final FilenameFilter originalFilter )
    {
        m_originalFilter = originalFilter;
    }
    public boolean accept( final File file, final String name )
    {
        return !m_originalFilter.accept( file, name );
    }
}

List file with file filter

import java.io.File;
import java.io.FileFilter;
public class MainClass {
  public static void main(String[] args) {
    File cwd = new File(System.getProperty("user.dir"));
    File[] htmlFiles = cwd.listFiles(new HTMLFileFilter());
    for (int i = 0; i < htmlFiles.length; i++) {
      System.out.println(htmlFiles[i]);
    }
  }
}
class HTMLFileFilter implements FileFilter {
  public boolean accept(File pathname) {
    if (pathname.getName().endsWith(".html"))
      return true;
    if (pathname.getName().endsWith(".htm"))
      return true;
    return false;
  }
}

This filter accepts Files that are directories

/****************************************************************
 * 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.                                           *
 ****************************************************************/

import java.io.File;
import java.io.FilenameFilter;
/**
 * This filter accepts <code>File</code>s that are directories.
 * Eg., here is how to print out a list of the current directory"s subdirectories:
 *
 * <pre>
 * File dir = new File(".");
 * String[] files = dir.list( new DirectoryFileFilter() );
 * for ( int i=0; i&lt;files.length; i++ )
 * {
 *     System.out.println(files[i]);
 * }
 * </pre>
 *
 * @author 
 * @version $Revision: 494012 $ $Date: 2007-01-08 11:23:58 +0100 (Mo, 08 Jan 2007) $
 * @since 4.0
 */
public class DirectoryFileFilter
    implements FilenameFilter
{
    public boolean accept( final File file, final String name )
    {
        return new File( file, name ).isDirectory();
    }
}