How to stop frame from closing in windowClosing event ?

Question

I have an application which will download some files from the web.
If the user attempts to close the applicaiton and if some files donwload action is in progress then i need to warn the user and prevent the window from closing. This is what i have done. But what happens is message box is displayed and my window is getting closed. How to get rid of this ? need your help...
frame.addWindowListener(new WindowAdapter() {
               public void windowClosing(WindowEvent we) {
                    if(DownloaderGUI.tableModel.isSomeThingDownloading()) {
                         JOptionPane.showMessageDialog(null,"cannot close when something is downloading");
                         return;
                    System.out.print("closing..");
                    backEndThread.setCanQuit(true);
                    cleanUp();
                    System.exit(0);
          });

Answer 1

I have also done a similar things but still window is getting closed.
public void actionPerformed(...)
if(!canquit) {
      return;
} else {
      System.exit(0);
}Message was edited by:
chaos_begins_here