playfair 加密算法的java实现，使用密码学的学生学习参考-Playfair encryption algorithm to achieve the java, the use of cryptography reference to student learning

本系统主要是针对用户和学生的，用户的信息是直接在注册的时候保存到数据库中的。(This system is mainly aimed at users and students, and the information of users is directly stored in the database when registered.)