因为以前多刷新几遍就莫名其妙的好了，所以一直以为是缓存问题。 但现在重启Tomcat, 重启MyEclipse，重启系统，清理缓存，清理临时文件，连注册表都清理，连TomCat能清理的都清理还是没用。 最后无奈重新定义了几个，还是不能用，在准备放弃前意外的发现之前 ...

It’s a 25-year-old principle of object-oriented (OO) design that you shouldn’t expose an object’s implementation to any other classes in the program. The program is unnecessarily difficult to maintain ...

Classes, fields, methods, constructors, and objects are the building blocks of object-based Java applications. This Java tutorial teaches you how to declare classes, describe attributes via fields, ...