Product Version = NetBeans IDE 8.0 Beta (Build 201401141042)
Operating System = Mac OS X version 10.9.1 running on x86_64
Java; VM; Vendor = 1.7.0_40
Runtime = Java HotSpot(TM) 64-Bit Server VM 24.0-b56

        int year, month, currentYear = 0;
        for(UserAccount userAccount: userAccounts) {
            registrationDate = Calendar.getInstance();
            registrationDate.setTime(userAccount.getRegistrationDate());
            if(currentYear == 0) {
                currentYear = registrationDate.get(Calendar.YEAR);
            }

            year = registrationDate.get(Calendar.YEAR) - currentYear;
            month = registrationDate.get(Calendar.MONTH);
            data[year][month] += 1;

            if(userAccount.getDeactivationDate() != null) {
                deactivationDate = Calendar.getInstance();
                deactivationDate.setTime(userAccount.getDeactivationDate());

                year = deactivationDate.get(Calendar.YEAR) - currentYear;
                month = deactivationDate.get(Calendar.MONTH);
                data[year][month] -= 1;
            }
        }

This sample was extracted from the class https://github.com/htmfilho/yougi/blob/master/src/main/java/org/cejug/yougi/web/report/MembershipGrowth.java. When I opened the project on Netbeans and opened this class the hint "Unused Assignment" appeared in the lines 114, 116, 122 and 123. However, the variables year and month are used  in the data array, so their values are actually used.