The toString() implementation of java.util.Date does not depend on the way the class is imported. It always returns a nice formatted date.
The toString() you see comes from another class.
Specific import have precedence over wildcard imports.
in this case
import other.Date
import java.util.*
new Date();
refers to other.Date and not java.util.Date.
The odd thing is that
import other.*
import java.util.*
Should give you a compiler error stating that the reference to Date is ambiguous because both other.Date and java.util.Date matches.