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I have a function in C++ as below.

void trackFilteredObject(int &x, int &y, cv::Mat threshold, cv::Mat cameraFeed){

    cv::Mat temp;
        threshold.copyTo(temp);
        vector< vector<cv::Point> > contours;
        vector<cv::Vec4i> hierarchy;
        findContours(temp, contours, hierarchy, CV_RETR_CCOMP, CV_CHAIN_APPROX_SIMPLE);
        double refArea = 0;
        bool objectFound = false;

        if (hierarchy.size() > 0) {
            vector< vector<cv::Point> > largestContourVec;
            largestContourVec.push_back(contours.at(contours.size() - 1));
            Eco_Rect = boundingRect(largestContourVec.at(0));
            int numObjects = hierarchy.size();
            if (numObjects<100){
                for (int index = 0; index >= 0; index = hierarchy[index][0]){
                    cv::Moments moment = moments((cv::Mat)contours[index]);
                    double area = moment.m00;
                    if (area>0 && area>refArea){
                        x = moment.m10 / area;
                        y = moment.m01 / area;
                        objectFound = true;
                        refArea = area;
                    }
                }

                if (objectFound == true){
                    cv::circle(cameraFeed, cv::Point(x, y), 10, cv::Scalar(0, 255, 0), 2);
                    line(cameraFeed, cv::Point(roi_rect.width / 2, 0), cv::Point(roi_rect.width / 2, roi_rect.height), 2, 2);
                    line(cameraFeed, cv::Point(0, roi_rect.height / 2), cv::Point(roi_rect.width,roi_rect.height / 2), 2, 2);
                }
            }
            else cv::putText(cameraFeed, "TOO MUCH NOISE! ADJUST FILTER", cv::Point(0, 50), 1, 2, cv::Scalar(0, 0, 255), 2);
        }

}

Then I want to convert it to Java to use in android.

void trackFilteredObject(int x, int y, Mat threshold, Mat cameraFeed){

    Mat temp = new Mat();
    threshold.copyTo(temp);
    List<MatOfPoint> contours = new ArrayList<MatOfPoint>();
    Mat hierarchy = new Mat();
    findContours(temp, contours, hierarchy, 2, 2);
    double refArea = 0;
    boolean objectFound = false;

    if (hierarchy.size() > 0) {
        List<MatOfPoint> largestContourVec = new ArrayList<MatOfPoint>();
        largestContourVec.add(contours.get(contours.size() - 1));
        Eco_Rect = boundingRect(largestContourVec.get(0));
        int numObjects = hierarchy.size();
        if (numObjects<100){
            for (int index = 0; index >= 0; index = hierarchy[index][0]){
                Moments moment = moments((Mat)contours.get(index));
                double area = moment.get_m00();
                if (area>0 && area>refArea){
                    x = (int) (moment.get_m10() / area);
                    y = (int) (moment.get_m01() / area);
                    objectFound = true;
                    refArea = area;
                }
            }

            if (objectFound == true){
                circle(cameraFeed, new Point(x, y), 10, new Scalar(0, 255, 0), 2);
                line(cameraFeed, new Point(roi_rect.width / 2, 0), new Point(roi_rect.width / 2, roi_rect.height),new Scalar(0,0,255), 2, 2);
                line(cameraFeed, new Point(0, roi_rect.height / 2), new Point(roi_rect.width,roi_rect.height / 2),new Scalar(0,0,255), 2, 2);
            }
        }
        else putText(cameraFeed, "TOO MUCH NOISE! ADJUST FILTER", new Point(0, 50), 1, 2, new Scalar(0, 0, 255), 2);
    }

}

However, i do not how to convert 3 lines coding that i commented due to different type of hierarchy in C++ and Java.

hierarchy.size() > 0 Error: cant compare org.opencv.core.Size with int. This one maybe can replace by hierarchy != null.

int numObjects = hierarchy.size(); Error: Basically same as above but i have no idea how to change it. I need to know the size.

for (int index = 0; index >= 0; index = hierarchy[index][0]) Error: In c++ hierarchy is vector type but in Java is Mat type.

Anyone can help me?