In Java the only place you can access a field directly without go through Class or object is in the code of that Class.
In classes other than the class where the field declare, you need to either using ClassA.fieldname (for static field) or objectA.fieldname (for non-static field),
However, if you are using jdk1.5 or higher, to access the field directly you might achieve static import.
Now, refer to jdk api documentation, you will find out that DAY_OF_WEEK is a static field of class Calendar
so to access a static field, you need to do this Calendar.Day_OF_WEEK (you might access from Calendar object e.g. myCalendar.DAY_OF_WEEK, but this is not encourage)
as stated above by using static import, import static java.util.Calendar.*.