That's all right if you don't want to sell your voucher
If you have not read anything(as you mentioned), then you might be in trouble. If you can spend some money, then go for paid mock exams like Enthuware or Whizlabs. If you can't spend any money, then you must go through Inquisition free mock exam and the Master Exam if you have the
SCJP study guide by Kathy Sierra and Bert Bates....