Java tutorial
/* * Copyright (c) 2006, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code 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 General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package javax.swing.filechooser; import java.io.File; import java.util.Locale; /** * An implementation of {@code FileFilter} that filters using a * specified set of extensions. The extension for a file is the * portion of the file name after the last ".". Files whose name does * not contain a "." have no file name extension. File name extension * comparisons are case insensitive. * <p> * The following example creates a * {@code FileNameExtensionFilter} that will show {@code jpg} files: * <pre> * FileFilter filter = new FileNameExtensionFilter("JPEG file", "jpg", "jpeg"); * JFileChooser fileChooser = ...; * fileChooser.addChoosableFileFilter(filter); * </pre> * * @see FileFilter * @see javax.swing.JFileChooser#setFileFilter * @see javax.swing.JFileChooser#addChoosableFileFilter * @see javax.swing.JFileChooser#getFileFilter * * @since 1.6 */ public final class FileNameExtensionFilter extends FileFilter { // Description of this filter. private final String description; // Known extensions. private final String[] extensions; // Cached ext private final String[] lowerCaseExtensions; /** * Creates a {@code FileNameExtensionFilter} with the specified * description and file name extensions. The returned {@code * FileNameExtensionFilter} will accept all directories and any * file with a file name extension contained in {@code extensions}. * * @param description textual description for the filter, may be * {@code null} * @param extensions the accepted file name extensions * @throws IllegalArgumentException if extensions is {@code null}, empty, * contains {@code null}, or contains an empty string * @see #accept */ public FileNameExtensionFilter(String description, String... extensions) { if (extensions == null || extensions.length == 0) { throw new IllegalArgumentException("Extensions must be non-null and not empty"); } this.description = description; this.extensions = new String[extensions.length]; this.lowerCaseExtensions = new String[extensions.length]; for (int i = 0; i < extensions.length; i++) { if (extensions[i] == null || extensions[i].length() == 0) { throw new IllegalArgumentException("Each extension must be non-null and not empty"); } this.extensions[i] = extensions[i]; lowerCaseExtensions[i] = extensions[i].toLowerCase(Locale.ENGLISH); } } /** * Tests the specified file, returning true if the file is * accepted, false otherwise. True is returned if the extension * matches one of the file name extensions of this {@code * FileFilter}, or the file is a directory. * * @param f the {@code File} to test * @return true if the file is to be accepted, false otherwise */ public boolean accept(File f) { if (f != null) { if (f.isDirectory()) { return true; } // NOTE: we tested implementations using Maps, binary search // on a sorted list and this implementation. All implementations // provided roughly the same speed, most likely because of // overhead associated with java.io.File. Therefor we've stuck // with the simple lightweight approach. String fileName = f.getName(); int i = fileName.lastIndexOf('.'); if (i > 0 && i < fileName.length() - 1) { String desiredExtension = fileName.substring(i + 1).toLowerCase(Locale.ENGLISH); for (String extension : lowerCaseExtensions) { if (desiredExtension.equals(extension)) { return true; } } } } return false; } /** * The description of this filter. For example: "JPG and GIF Images." * * @return the description of this filter */ public String getDescription() { return description; } /** * Returns the set of file name extensions files are tested against. * * @return the set of file name extensions files are tested against */ public String[] getExtensions() { String[] result = new String[extensions.length]; System.arraycopy(extensions, 0, result, 0, extensions.length); return result; } /** * Returns a string representation of the {@code FileNameExtensionFilter}. * This method is intended to be used for debugging purposes, * and the content and format of the returned string may vary * between implementations. * * @return a string representation of this {@code FileNameExtensionFilter} */ public String toString() { return super.toString() + "[description=" + getDescription() + " extensions=" + java.util.Arrays.asList(getExtensions()) + "]"; } }