Hi,
I am developing an application which needs to dynamically show whether a host is up or down.I have used buttons on which i am pasting the icon indicating up or down.So, when a node is down, I am replacing the icon that indicates up with the icon that indicates down using setIcon() function.But instead of changing the icon a NullPointerExce ption is generated.For example,

private JButton c1;
JButton c1 = new JButton();...