【Java】System.in报错The type java.io.InputStream cannot be resolved. It is indirectly refer...解决办法

可以看到两个error

The project was not built since its build path is incomplete. Cannot find the class file for java.io.InputStream. Fix the build path....

The type java.io.InputStream cannot be resolved. It is indirectly referenced from required type java.lang.System

原因本人还没弄清楚，有清楚的可以评论区分享一下

解决办法：

右键.java文件然后点击Source-Format