为什么OpenCV的detectMultiScale3函数会挂起我的程序？

Question

我正在玩OpenCV Java，我决定看看是否可以通过运行detectMultiScale3函数输出OpenCV的CascadeClassifier返回的置信度值。我的代码如下：

//...
if (this.capture.isOpened())
{
    this.cameraActive = true;
    // grab a frame every 33 ms (30 frames/sec)
    Runnable frameGrabber = new Runnable() {
        @Override
        public void run()
        {
            // run a couple of iterations before you process the faces
            for(int i = 0; i < 3; i++) {
                // effectively grab and process a single frame
                Mat frame = grabFrame();
                MatOfInt rl = new MatOfInt();
                MatOfDouble lw = new MatOfDouble();
                if(i == 0) {
                    classifier.detectMultiScale3(frame, faces, rl, lw);
                    eyeclass.detectMultiScale(frame, eyes);
                }
                for(Rect rect : faces.toArray()) {
                    Imgproc.rectangle(
                        frame,
                        new Point(rect.x, rect.y),
                        new Point(rect.x + rect.width, rect.y + rect.height),
                        new Scalar(255, 0, 0),
                        5
                    );
//                  String print = Double.toString(values[i]);
//                  Imgproc.putText(frame, print, new Point(rect.x, rect.y), 0, 0.5, new Scalar(255, 255, 255));
                }
                for(Rect rect : eyes.toArray()) {
                    Imgproc.rectangle(
                        frame,
                        new Point(rect.x, rect.y),
                        new Point(rect.x + rect.width, rect.y + rect.height),
                        new Scalar(0, 0, 255),
                        2
                    );
                }
                // convert and show the frame
                Image imageToShow = mat2Image(frame);
                updateImageView(currentFrame, imageToShow);
            }
        }
    };

    this.timer = Executors.newSingleThreadScheduledExecutor();
    this.timer.scheduleAtFixedRate(frameGrabber, 0, 99, TimeUnit.MILLISECONDS);

    // update the button content
    this.button.setText("Stop Camera");
}

每当我仅用detectMultiScale3替换detectMultiScale函数时，该程序便会运行，但是每当我使用detectMultiScale3时，该程序就会特别挂在该函数上。为什么有任何原因，还是我只是错误地使用了此功能？