When Martin Wiernsperger was a graduate student, he and fellow student Mackenzie Feinberg realized they both had family members in the health care field—and both had heard relatives complain about ...

When Martin Wiernsperger was a graduate student, he and fellow student Mackenzie Feinberg realized they both had family members in the healthcare field – and both had heard relatives complain about ...

本内容遵循CC 4.0 BY-SA版权协议 从 Java 语法角度来看，这并不一定报错。 但是从业务逻辑来看，学生年龄显然不应该是负数。 这就引出了 Java 面向对象中的一个核心思想： 封装（Encapsulation）。