Sort files by the extensionTag(s): IO
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()); // } } }
Take a look at this HowTo to sort the filenames in ascending/descending order (based on the last modified timestamp).