method tri imag icon given known locat file extens us imag file known extens param resourc imag look param desc descript imag icon param loader loader us load resourc imag icon given imag imag icon lookup icon resourc resourc desc loader loader resourc java identifi resourc cach resourc imag icon resourc cach resourc imag icon re java net url img url lookup icon url resourc loader img url re imag icon img url desc resourc cach resourc cach resourc re re 