In IntelliJ IDEA, a class or method has been called, but it shows is never used when clicked

Reprinted at: https://blog.csdn.net/qq_27276045/article/details/103277016
Some classes and methods in IntelliJ IDEA are obviously called by other classes or methods, but when you look at them, they are grayed out and the mouse is placed The above shows: Class'XXX' is never used or Method'XXX' is never used, and there is no problem when running.

Solution: File—>Invalidate Caches/Restart