Here you can find the source of weekDay(final Date date)
public static int weekDay(final Date date)
//package com.java2s; //License from project: Apache License import java.util.Calendar; import java.util.Date; import java.util.GregorianCalendar; import static java.util.Calendar.*; public class Main { public static int weekDay(final Date date) { return fromDateToCalendar(date).get(DAY_OF_WEEK); }// w w w . ja v a2s . com public static Calendar fromDateToCalendar(final Date date) { final Calendar cal = new GregorianCalendar(); cal.clear(); cal.setMinimalDaysInFirstWeek(4); cal.setFirstDayOfWeek(Calendar.MONDAY); cal.setTime(date); return cal; } }