问提高文件搜索和MediadataRetriever的性能

EN

final File[] ArrayOfFiles = mysteriousFunction(); //returns a ton of files
final MediaMetadataRetriever iLoveThisThing = new MediaMetadataRetriever();

ArrayList<File> audioFiles = new ArrayList<>();

for (File file : ArrayOfFiles)
            {
                final String fileString = file.toString();

                String extension = "";
                final int lastIndexOfDot = fileString.lastIndexOf('.');
                final int lastIndexOfSeperator = fileString.lastIndexOf(File.separatorChar);
                if (lastIndexOfDot > lastIndexOfSeperator)
                {
                    extension = fileString.substring(lastIndexOfDot + 1);

                }

                switch (extension)
                {
                    case "mp3":
                    case "mp4":
                    case "3gp":
                    case "m4a":
                    case "aac":
                    case "ogg":
                    case "wav":
                    case "mid":
                    case "ts":
                    case "imy":
                    case "flac":
                    case "xmf":
                    case "mxmf":
                    case "mkv":
                        iLoveThisThing.setDataSource(fileString);
                        final String foo1 = iLoveThisThing.extractMetadata(MediaMetadataRetriever.METADATA_KEY_MIMETYPE);
                        if (foo1 != null)
                        {
                            String foo2 = foo1.substring(0, foo1.indexOf('/'));
                            if (foo2.equals("audio"))
                            {
                                audioFiles.add(file);
                            }
                        }
                        break;
                    default:
                        break;
                }
            }

private static final Set<String> extensions = new HashSet<>(Arrays.asList("mp3", "mp4", "3gp", "m4a", "aac", "ogg", "wav", "mid", "ts", "imy", "flac", "xmf", "mxmf", "mkv"));

public static void DoStuff()
{
    new Thread(() -> {
        final File[] allFiles = get_a_ton_of_files();
        final Set<File> audioFilesSet = ConcurrentHashMap.newKeySet(allFiles.length);
        Arrays.stream(allFiles).parallel().forEach(file -> {
            final String fileString = file.toString();
            final int lastIndexOfDot = fileString.lastIndexOf('.');
            if (lastIndexOfDot > fileString.lastIndexOf(File.separatorChar))
            {
                final String extension = fileString.substring(lastIndexOfDot + 1);
                if (extensions.contains(extension))
                {
                    final MediaMetadataRetriever myMediadataRetriever = new MediaMetadataRetriever();
                    myMediadataRetriever.setDataSource(fileString);
                    final String mime = myMediadataRetriever.extractMetadata(MediaMetadataRetriever.METADATA_KEY_MIMETYPE);
                    if (mime != null && mime.startsWith("audio"))
                    {
                        audioFiles.add(file);
                    }
                    myMediadataRetriever.release();
                }
            }
        });
    }).start();
}