c++ to java

edit

yes, I am using List<MatOfPoint>. but I need to calculate it's size

void MarkerDetector::findContours(const cv::Mat& thresholdImg,std::vector<std::vector<cv::Point>>& contours,int minContourPointsAllowed)
{
    std::vector< std::vector<cv::Point> > allContours;
    cv::findContours(thresholdImg, allContours, CV_RETR_LIST, CV_CHAIN_APPROX_NONE);
    contours.clear();
    for (size_t i=0; i<allContours.size(); i++)
    {
        int contourSize = allContours[i].size();
        if (contourSize > minContourPointsAllowed)
        {
            contours.push_back(allContours[i]);
        }
    }
}