OpenCV for Android - Access elements of Mat

private Mat featuresVectorBinarization(Mat fv){

    int size = (int) fv.total() * fv.channels();
    double[] buff = new double[size];
    fv.get(0, 0, buff);

    for(int i = 0; i < size; i++)
    {
        buff[i] = (buff[i] >= 0) ? 1 : 0;
    }

    Mat bv = new Mat(fv.size(), CvType.CV_8U);
    bv.put(0, 0, buff);
    return bv;
}