Application icon on window list applet in Gnome desktop

[Qihua Wang <qihua wang alcatel com>]

Hi,
Application listed on window list applet has icon on the left side and window title text occupies the rest of the space.
For some applications, the icons are shown as blank square as default.
Does anybody know how to set the icon with your application so that the icon is shown on the window list applet.
I have an application developed in Java, I have minimized icon for it, it runs on CDE or openwin desktop on Solaris shown the 
minimized icon perfectly. But switch to gnome, the icon doesn't show on the window list applet.

Thanks!

-Qihua