How to Make a Directory in SDCARD

public String getFilename() {

    filepath = Environment.getExternalStorageDirectory().getPath();

    file = new File(filepath, "Hair");

    if (!file.exists()) {
        file.mkdirs();
    }

        return (file.getAbsolutePath() + "/"
            + String.valueOf(System.currentTimeMillis()) + ".png");
}