IDEA 报错 Package 'java.util' is declared in module 'java.base', which is not in the module graph

在 IDEA 中更改了 JDK 版本之后报错：Package 'java.util' is declared in module 'java.base', which is not in the module graph，项目中的所有 java.util 和 java.lang 包的代码全部带红色波浪线...

解决方法：清理 IDEA 缓存：
File -> Invalidate caches -> select "Clear file system cache and Local history" -> Invalidate and Restart

本文来源：gradle - Kotlin + Java 9 modules: Module java.base cannot be found in the module graph - Stack Overflow