Re: heap memory issue, related with garbage collection

Thank you for all your replies.

My original post missed some information which now is critical. My program =
has two buttons besides other buttons: one button is "Next" and one button =
is "ContinueouslyPlay". When clicking button "ContinueouslyPlay", a child t=
hread is repeatedly calling displayPic() with incremented parameter. The co=
de above works well since all the variables are local - so the thread 'see'=
 the new objects without problem. The problem is out of heap memory when re=
aching picture 150.(If clicking "Next" button, it is the main thread displa=
ying next picture only - very simple.)

Now, I have changed those variables to class instance variables. Now concur=
rent programming adds the complexity: in "ContinueouslyPlay" mode, very oft=
en the displayed one remain unchanged for quite a bit even though the title=
 is showing the next, next etc picture file names. So the child thread does=
 not 'see' the new stuff. I have added 'volatile' keyword to the instance v=
ariables. No help. There is no out of heap memory error any more. But such =
no displaying is more annoying. Here is the code(I think using a separate t=
hread for "ContinueouslyPlay" mode is reasonable and I don't want to change=
 it. Otherwise all other buttons are not responsive):

public class PictureDisplayer implements ActionListener {
    private final JFrame _jFrame;
    private final JPanel _jPanel;
    private volatile JLabel _picLabel;
    private volatile JPanel _picPanel;
    private volatile ImageIcon _imageIcon;
    ..
   public PictureDisplayer() throws Exception
    {
        _jFrame = new JFrame();
        _jFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        _jFrame.setSize(Constants.MONITOR_WIDTH, Constants.MONITOR_HEIGHT);
        _jPanel = new JPanel(new BorderLayout());
        //Create the toolbar.
        final JToolBar toolBar = new JToolBar("Still draggable");

        //Lay out the main panel.
        _jPanel.setPreferredSize(new Dimension(Constants.MONITOR_WIDTH, Con=
stants.MONITOR_HEIGHT));
        _jPanel.add(toolBar, BorderLayout.PAGE_START);
        _picLabel = new JLabel();
        _picPanel = new JPanel();

        _runThread = new Thread(new Runnable() {
            public void run() {
                while(true) {
                    displayPic(++_picCount);
                    try {
                        Thread.sleep(10000);
                    }
                    catch(final Exception e) {//hopefully never happen
                    }
                }
            }
        });
        ..
    }

    private void displayPic(final int picCount)
    {
        String pngFileNameWithPath = xxx; //create PNG file name from pic=
Count

         _imageIcon = new ImageIcon(pngFileNameWithPath);
        _picLabel.setIcon(_imageIcon);
        _picPanel.add(_picLabel);
        _jPanel.add(_picPanel, BorderLayout.CENTER);
        _jFrame.getContentPane().add(_jPanel);
        _jFrame.setTitle(pngFileNameWithPath);
        _jFrame.setVisible(true);
    }

   public void actionPerformed(final ActionEvent evt) {
    ..
   }
}

Thank you very much.