FIle dir to list

file_list.java

void ================================================
File dir = new File ("data/user/VRP");
                List<File> files = null;
                try {
                   files = getFileListing(dir);
                } catch (FileNotFoundException e) {
                    e.printStackTrace();
                }
======================================================
static public List<File> getFileListing(
            File aStartingDir
    ) throws FileNotFoundException {
        validateDirectory(aStartingDir);
        List<File> result;
        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);
        }
    }