Using the latest version of eclipse, you may encounter such a problem (error report)

“Must declare a named package because this compilation unit is associated to the named module ‘xxx'”
the reason for this is that in the latest version of eclipse, the package needs to be defined while defining a class.

How to define a package:

In the eclipse menu bar, select File – & gt; New-> Class command, in the Import dialog box, find the package, and then name it（ The position of the red line cannot be empty)