FilenameFilter学习

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从给定的一个路径中筛选中某种格式的文件，通常的做法，便是遍历该目录，然后按照文件后缀来判断该文件是否符合判断条件。

public class FileFilter {public static void main(String[] args) {File filepath = new File("F:\\论文\\中国知网论文\\中国知网论文");List<File> list = filterFile(filepath);System.out.println(list.size());}public static List<File> filterFile(File file) {List<File> list = new ArrayList<File>();File[] fileList = file.listFiles();for (int i = 0; i < fileList.length; i++) {// 判断该file是否是目录，是目录，则继续深入遍历if (fileList[i].isDirectory()) {filterFile(fileList[i]);// 是文件时，判断后缀是否是PDF结尾，是则截取出来该文件} else if (fileList[i].getName().endsWith(".pdf")) {list.add(fileList[i]);}else continue;}return list;}}

其实 java的File 类有一个自带的过滤方法，即FilenameFilter接口

FilenameFilter接口自带一个accept方法，过滤符合条件的文件类型

package java.io;/** * Instances of classes that implement this interface are used to * filter filenames. These instances are used to filter directory * listings in the <code>list</code> method of class * <code>File</code>, and by the Abstract Window Toolkit's file * dialog component. * * @author  Arthur van Hoff * @author  Jonathan Payne * @see     java.awt.FileDialog#setFilenameFilter(java.io.FilenameFilter) * @see     java.io.File * @see     java.io.File#list(java.io.FilenameFilter) * @since   JDK1.0 */public interface FilenameFilter {    /**     * Tests if a specified file should be included in a file list.     *     * @param   dir    the directory in which the file was found.     * @param   name   the name of the file.     * @return  <code>true</code> if and only if the name should be     * included in the file list; <code>false</code> otherwise.     */    boolean accept(File dir, String name);}

FilenameFilter 接口中的accept方法，主要判断给定的文件是否包含在该目录中

通过FilenameFilter 接口改造后的代码

public class FileFilter {public static void main(String[] args) {File filepath = new File("F:\\论文\\中国知网论文\\中国知网论文");List<File> list = filterFile(filepath);System.out.println(list.size());}public static List<File> filterFile(File file) {// 定义变量list来接收最后的文件列表List<File> list = new ArrayList<File>();// 将文件类型给到FilterName 中FilterName filter = new FilterName(".abcd"); // 文件过滤        String[] files = file.list(filter);                  // 由于File.list(FilenameFilter filter) 返回结果为数组        // 此处将数组转换为list        if (null != files) {            for (String fileName : files) {            list.add(new File(fileName));            }        }return list;}}class FilterName implements FilenameFilter {    private String type;    // 构造方法，定义要过滤的文件类型    FilterName(String type) {    this.type = type;    }    @Overridepublic boolean accept(File dir, String name) {return name.endsWith(type);}}

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