opencv mat.at<cv::Vec4b> convert to java

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Hello I have opencv code written on objective-c I dont know how to convert it on java..

The objective c code looks like this.

cv::Math image2 = .....

for(int x = image2.cols; x >= 0; --x){
  for(int y = 0; y < image2.rows; y++) {
     int red = image2.at<cv::Vec4b>(y,x)[0];
     int green = image2.at<cv::Vec4b>(y,x)[1];
     int blue = image2.at<cv::Vec4b>(y,x)[2];

    //to set the pixel
     //image2.at<cv::Vec4b>(y,x)[0] = 100;
     //image2.at<cv::Vec4b>(y,x)[1] = 0;
     //image2.at<cv::Vec4b>(y,x)[2] = 200;
  }
}

Any help? I need java version of this code.