get filename from url in android not working

Question

I can get file name of in sd card with this way

List<File> files = getListFiles(new File(sdcard/Download/));

and it work fine but i want get names from server and this is my try so far :

public class MainActivity extends AppCompatActivity {


    URL url;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        try {
            url = new URL("www.memaraneha.ir/Erfan/");
        } catch (MalformedURLException e) {
            e.printStackTrace();
        }

        List<File> files = getListFiles(new File(url.getPath()));

        Log.d("list :", String.valueOf(files));
    }

    private List<File> getListFiles(File parentDir) {
        ArrayList<File> inFiles = new ArrayList<File>();
        File[] files = parentDir.listFiles();
        for (File file : files) {
            if (file.isDirectory()) {
                inFiles.addAll(getListFiles(file));
            } else {
                if(file.getName().endsWith(".mp3")){
                    inFiles.add(file);
                }
            }
        }
        return inFiles;
    }

}

but it not working and i think some thing is wrong ...if any one can please help