Every so often I need to run java based programs or programs that use a java based front end. For example I occasionally need to fire up openoffice, matlab, mathematica, ireports and almost everytime I forget what environment variables to try and set to get the interfaces working properly under DWM

So try

export AWT_TOOKIT=MToolkit
./app

or

wmname LG3D
unset AWT_TOOLKIT
./app

Usually one or the other will work. If not I usually just start up Xnest or a secondary Xserver running a different windowmanger to run that one application. Note, wmname is a suckless.org tool.