Try this:
mytable.addMouseListener(new MouseAdapter() {
public void mousePressed(MouseEvent mouseEvent) {
JTable table =(JTable) mouseEvent.getSource();
Point point = mouseEvent.getPoint();
int row = table.rowAtPoint(point);
if (mouseEvent.getClickCount() == 2 && table.getSelectedRow() != -1) {
// your valueChanged overridden method
}
}
});