Problems with AddCommand

I tried to execute the following code but I am getting errors 
Can u explain why?
 
AddCommand ac=new AddCommand();
ac.setBuilder(null);
File f[]=new File[1];
f[0]=new File(cvsClient.getLocalPath()+"/Upload/","sample.txt");
ac.setFiles(f);
cvsClient.executeCommand(ac,go);
 
I am getting unrecognized request error