Recently, Java has been spread widely. However, Java has a problem that an attacker can reconstruct Java source codes from Java classfiles. Therefore many techniques for protecting Java software have been proposed, but, quantitive security evaluations are not fully given. This paper proposes an obfuscation scheme for Java source codes by destructing the encapsulation. In addition, we propose an evaluation scheme on the number of accesses to the fields and the methods of the other classes. We try to realize tamper-resistant software with the certain quantitive basis of security using our evaluation.