I used JFrame and want to add windowlistener to a JFrame object.I overrided the windowClosing method in windowAdapter.But I don't want the JFrame object always closed. I want the system will exit in some cases,and the system won't in other cases.
My code:


this.addWindowListener(new java.awt.event.WindowAdapter() {
public void windowClosing(java.awt.event.WindowEvent e){
if (isModified==true) { //there are some changes of the file
String message="Your file has been modified，do you want to save the changes?";
int result=JOptionPane.showConfirmDialog(this, message, "save?", JOptionPane.YES_NO_CANCEL_OPTION );
if (result==JOptionPane.CANCEL_OPTION) { //don't exit
return; //don't really exit
} else if (result==JOptionPane.YES_OPTION){ //
save(); //the save block
}else { //I dont want to save the changes
System.exit(0);
}
}else { // there are't any changes of the file
System.exit(0);
}
}
});


I watched the task manager.In fact,if just override the windowClosing method while do nothing in the method ,such as:



this.addWindowListener(new java.awt.event.WindowAdapter() {
public void windowClosing(java.awt.event.WindowEvent e){

}
});



The frame don't really been killed but it still owns resources, but I can't see the JFrame object.
Can anyone tell me the reason? How can I kill the frame in some cases when the windowClosing method is called while the freme is not killed and can be seen in some cases?
Thanks!