Java implements a recursive file list method

This article illustrates how Java implements a recursive list of files. Share with you for your reference. The details are as follows:

FileListing. Java is as follows:

import java.util.*;
import java.io.*;

public final class FileListing {
 /**
 * Demonstrate use.
 * 
 * @param aArgs - <tt>aArgs[0]</tt> is the full name of an existing 
 * directory that can be read.
 */
 public static void main(String... aArgs) throws FileNotFoundException {
  File startingDirectory= new File(aArgs[0]);
  List<File> files = FileListing.getFileListing(startingDirectory);
  //print out all file names, in the the order of File.compareTo()
  for(File file : files ){
   System.out.println(file);
  }
 }
 
 static public List<File> getFileListing(
  File aStartingDir
 ) throws FileNotFoundException {
  validateDirectory(aStartingDir);
  List<File> result = getFileListingNoSort(aStartingDir);
  Collections.sort(result);
  return result;
 }
 // PRIVATE //
 static private List<File> getFileListingNoSort(
  File aStartingDir
 ) throws FileNotFoundException {
  List<File> result = new ArrayList<File>();
  File[] filesAndDirs = aStartingDir.listFiles();
  List<File> filesDirs = Arrays.asList(filesAndDirs);
  for(File file : filesDirs) {
   result.add(file); //always add, even if directory
   if ( ! file.isFile() ) {
    //must be a directory
    //recursive call!
    List<File> deeperList = getFileListingNoSort(file);
    result.addAll(deeperList);
   }
  }
  return result;
 }
 
 static private void validateDirectory (
  File aDirectory
 ) throws FileNotFoundException {
  if (aDirectory == null) {
   throw new IllegalArgumentException("Directory should not be null.");
  }
  if (!aDirectory.exists()) {
   throw new FileNotFoundException("Directory does not exist: " + aDirectory);
  }
  if (!aDirectory.isDirectory()) {
   throw new IllegalArgumentException("Is not a directory: " + aDirectory);
  }
  if (!aDirectory.canRead()) {
   throw new IllegalArgumentException("Directory cannot be read: " + aDirectory);
  }
 }
}

I hope this article has been helpful to your Java programming.