Obfuscating problem when import jar file in project

Hello I am creating a j2me polish project which jar size is very high as i am using j2me polish so i nee开发者_开发问答d to obfuscate the jar files

everything is work perfect but now i need to include one external jar file in my project so as i am doing obfuscating using Proguard it is creating classes like a.class, b.class

so when my code reach to line where i use that external jar file giving me following error

No Class Def Found Error java.lang.NoClassDefFoundErro

MypackageName.MyClassname

For more clarification

i am using eclips, compiling files using ant then copy those compiled file in wtk scr, build in wtk and after that using proguard doing obfuscating.

how to solve this problem??

Did you use / understand the keep option of Proguard ?