以解析证书为例，了解JAVA中证书类及相关函数的用法。程序功能 是调用 JAVA安全API系列函数解析一个证书文件，获取相关信息-To resolve the certificate, for example, understand the JAVA classes and related functions of Certificate usage. Program function is to call the JAVA security API family functions parse a certificate file, access to relevant information