IDEA is referring to package-private visibility.
A class may be declared with the modifier
public, in which case that class is visible to all classes everywhere. If a class has no modifier (the default, also known as package-private), it is visible only within its own package
For more information, see Controlling Access to Members of a Class.
You can solve the problem by removing public keyword from the class (if the class is not intended to be used outside the package), or by using the class from a different package.