How to display image on JAVA release

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Window management from OpenCV highgui module is no wrapper to Java yet. You need to use some Java UI frameworks like SWING or wrap it to Java manually using JNI.

You can use the next code to transform a cvMat element into a java element: BufferedImage or Image:

    public BufferedImage Mat2BufferedImage(Mat m){
// source: http://answers.opencv.org/question/10344/opencv-java-load-image-to-gui/
// Fastest code
// The output can be assigned either to a BufferedImage or to an Image

    int type = BufferedImage.TYPE_BYTE_GRAY;
    if ( m.channels() > 1 ) {
        type = BufferedImage.TYPE_3BYTE_BGR;
    }
    int bufferSize = m.channels()*m.cols()*m.rows();
    byte [] b = new byte[bufferSize];
    m.get(0,0,b); // get all the pixels
    BufferedImage image = new BufferedImage(m.cols(),m.rows(), type);
    final byte[] targetPixels = ((DataBufferByte) image.getRaster().getDataBuffer()).getData();
    System.arraycopy(b, 0, targetPixels, 0, b.length);  
    return image;

}

And then display it with:

    public void displayImage(Image img2)
{   
    //BufferedImage img=ImageIO.read(new File("/HelloOpenCV/lena.png"));
    ImageIcon icon=new ImageIcon(img2);
    JFrame frame=new JFrame();
    frame.setLayout(new FlowLayout());        
    frame.setSize(img2.getWidth(null)+50, img2.getHeight(null)+50);     
    JLabel lbl=new JLabel();
    lbl.setIcon(icon);
    frame.add(lbl);
    frame.setVisible(true);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

}