Android : migrate C++ code to Java (Oencv + Android)?

I'm trying to detect bounding boxes with OpenCV+Android. But the tutorial is in C++ and I want to migrate it to Java:

  vector<vector<Point> > contours;
  vector<Vec4i> hierarchy;    
  /// Detect edges using Threshold
  threshold( src_gray, threshold_output, thresh, 255, THRESH_BINARY );
  /// Find contours
  findContours( threshold_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0) );  
 //up to this converted      //........................................................................

  /// Approximate contours to polygons + get bounding rects and circles
  vector<vector<Point> > contours_poly( contours.size() );
  vector<Rect> boundRect( contours.size() );
  vector<Point2f>center( contours.size() );
  vector<float>radius( contours.size() );    
  for( int i = 0; i < contours.size(); i++ )
     { approxPolyDP( Mat(contours[i]), contours_poly[i], 3, true );
       boundRect[i] = boundingRect( Mat(contours_poly[i]) );
       minEnclosingCircle( (Mat)contours_poly[i], center[i], radius[i] );
     }    
  /// Draw polygonal contour + bonding rects + circles
  Mat drawing = Mat::zeros( threshold_output.size(), CV_8UC3 );
  for( int i = 0; i< contours.size(); i++ )
     {
       Scalar color = Scalar( rng.uniform(0, 255), rng.uniform(0,255), rng.uniform(0,255) );
       drawContours( drawing, contours_poly, i, color, 1, 8, vector<Vec4i>(), 0, Point() );
       rectangle( drawing, boundRect[i].tl(), boundRect[i].br(), color, 2, 8, 0 );
       circle( drawing, center[i], (int)radius[i], color, 2, 8, 0 );
     }

I've managed to find the contours (see the following code) and now I need help with detecting the object.

    Imgproc.cvtColor(ImageMatin, ImageMatBk, Imgproc.COLOR_RGB2GRAY,8);
    //Sobel operator in horizontal direction.                       
    Imgproc.Sobel(ImageMatBk,ImageMatout,CvType.CV_8U,1,0,3,1,0.4,Imgproc.BORDER_DEFAULT);
    //Converting GaussianBlur                   
   Imgproc.GaussianBlur(ImageMatout, ImageMatout, new Size(5,5),2); 

    Imgproc.threshold(ImageMatout, ImageMatout, 0, 255, Imgproc.THRESH_OTSU);

    ArrayList<MatOfPoint> contours = new ArrayList<MatOfPoint>();
    Imgproc.findContours(ImageMatout, contours, new Mat(), Imgproc.RETR_TREE, Imgproc.CHAIN_APPROX_SIMPLE);