今天不研究书上的内容，在网上研究一下java的输入输出函数。
输出函数很简单，直接调用System类的out对象的print函数即可。
输入函数，https://blog.csdn.net/csdn0125/article/details/80880705?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522159842708119724811826250%2522%252C%2522scm%2522%253A%252220140713.130102334..%2522%257D&request_id=159842708119724811826250&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2~all~first_rank_ecpm_v3~pc_rank_v3-2-80880705.pc_ecpm_v3_pc_rank_v3&utm_term=java%E8%BE%93%E5%85%A5%E8%BE%93%E5%87%BA%E5%87%BD%E6%95%B0&spm=1018.2118.3001.4187
https://blog.csdn.net/jimha147/article/details/8594488?biz_id=102&utm_term=java%E8%BE%93%E5%85%A5%E5%87%BD%E6%95%B0&utm_medium=distribute.pc_search_result.none-task-blog-2~all~sobaiduweb~default-1-8594488&spm=1018.2118.3001.4187
输入单个字符的两种方法。
https://blog.csdn.net/zjhzcjg/article/details/83271149