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【Java】根据扩展名对文件排序代码

作者:Dezai.CN / 发布于2013/7/1/ 663

根据扩展名对文件排序代码


	dirlist_by_extension(Dir) ->
	 case file:list_dir(Dir) of
	 {ok, Filenames} ->
	 F = fun(Name) ->
	 Ext = string:to_lower(filename:extension(Name)),
	 {Ext, Name}
	 end,
	 List = lists:sort(lists:map(F, Filenames)),
	 [Name || {_, Name} <- List];
	 {error, enoent} ->
	 io:format("The directory(~s) does not exist.~n", [Dir]),
	 ng
	 end.

	

	

	import java.io.*;
	import java.util.Arrays;
	import java.util.ArrayList;
	import java.util.List;
	import java.util.Comparator;

	public class FileUtils{

	 /**
	 * returns a folder content sorted by extension
	 * case-insensitive ,ascending order
	 * subfolders are not included
	 * @param folder folder name
	 * @return
	 * @throws IOException if not a folder or not found
	 */
	 @SuppressWarnings("unchecked")
	 public static File[] dirListByExtension(File folder) throws IOException {
	 if (!folder.isDirectory() || !folder.exists()) {
	 throw new IOException( folder.getName() + " : Not a folder or not exist");
	 }
	 File files[] = FileUtils.list(folder, false); // don't include subfolder
	 Arrays.sort(files, new Comparator() {
	 public int compare(final Object o1, final Object o2) {
	 String s1 = ((File) o1).getName().toLowerCase();
	 String s2 = ((File) o2).getName().toLowerCase();
	 final int s1Dot = s1.lastIndexOf('.');
	 final int s2Dot = s2.lastIndexOf('.');
	 //
	 if ((s1Dot == -1) == (s2Dot == -1)) { // both or neither
	 s1 = s1.substring(s1Dot + 1);
	 s2 = s2.substring(s2Dot + 1);
	 return s1.compareTo(s2);
	 } else if (s1Dot == -1) { // only s2 has an extension, so s1 goes first
	 return -1;
	 } else { // only s1 has an extension, so s1 goes second
	 return 1;
	 }
	 }
	 });
	 return files;
	 }

	 /**
	 * returns the content of a folder with subfolders included or not
	 * @param folder folder name
	 * @param includeSubFolder true/false
	 * @return array of files
	 */
	 public static File[] list(File folder, boolean includeSubFolder) {
	 if (!folder.isDirectory()) {
	 return null;
	 }
	 File files[] = folder.listFiles();
	 List<File> list = new ArrayList<File>();
	 for (File file : files) {
	 if (file.isDirectory()) {
	 if (includeSubFolder) {
	 list.add(file);
	 }
	 }
	 else {
	 list.add(file);
	 }
	 }
	 if (list.isEmpty()) {
	 return null;
	 }
	 return list.toArray(new File[]{});
	 }

	 /*
	 * TEST
	 */
	 public static void main(String args[]) throws Exception {
	 File files[] = FileUtils.dirListByExtension(new File("C:/temp"));
	 for (File file : files) {
	 System.out.println(file.getName());
	 }
	 // to reverse
	 // List<File> temp = Arrays.asList(files);
	 // java.util.Collections.reverse(temp);
	 // files = temp.toArray(new File[]{});
	 // for (File file : files) {
	 /// System.out.println(file.getName());
	 // }

	 }

	}

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