Util.java

package by.fksis.schedule;

import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;

@SuppressWarnings("deprecation")
public final class Util {
    public static int getWeek(Date date) {
        Date januaryFirst = new Date(date.getYear(), 0, 1);
        return (int) Math.round(Math.ceil((((date.getTime() - januaryFirst.getTime()) / 86400000) + januaryFirst.getDay() + 1) / 7));
    }

    public static int getLastEnteringYear() {
        int year = new GregorianCalendar().get(GregorianCalendar.YEAR);
        if (new Date().getMonth() < 8)
            year--;
        return year;
    }

    public static int getScheduleWeek(Date date) {
        Calendar sep1 = new GregorianCalendar(getLastEnteringYear(), GregorianCalendar.SEPTEMBER, 1);
        if (sep1.get(GregorianCalendar.DAY_OF_WEEK) == GregorianCalendar.SUNDAY) {
            sep1.add(GregorianCalendar.DAY_OF_YEAR, -7);
        }
        sep1.add(GregorianCalendar.DAY_OF_YEAR, -sep1.get(GregorianCalendar.DAY_OF_WEEK) + GregorianCalendar.MONDAY);
        Calendar now = new GregorianCalendar();
        now.setTime(date);

        int dWeeks = (int) Math.floor((now.getTime().getTime() - sep1.getTime().getTime()) / 86400000 / 7);
        return dWeeks % 4 + 1;
    }

    public static int getDayOfWeekIndex(Calendar date) {
        switch (date.get(Calendar.DAY_OF_WEEK)) {
            case Calendar.SUNDAY:
                return 6;
            case Calendar.MONDAY:
                return 0;
            case Calendar.TUESDAY:
                return 1;
            case Calendar.WEDNESDAY:
                return 2;
            case Calendar.THURSDAY:
                return 3;
            case Calendar.FRIDAY:
                return 4;
            case Calendar.SATURDAY:
                return 5;
        }
        return 0;
    }

    public static <T> T defaultValue(T obj, T def) {
        return (obj == null) ? def : obj;
    }
}