day_of_the_week.java

public String dayOfTheWeek(int day, int month, int year) {
    String[] days = new String[]{"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};
    int k = day;
    int m = month < 3 ? month + 10 : month - 2;
    int d = month < 3 ? (year % 100) - 1 : (year % 100);
    int c = year / 100;
    double f = k + Math.floor((13.0 * m - 1.0) / 5.0) + d + Math.floor(d / 4.0) + Math.floor(c / 4.0) - 2.0 * c;
    int rem = (int) f % 7;
    if (rem < 0) {
        rem = 7 + rem;
    }
    return days[rem];
}