UtilDayOfWeek.java

import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.regex.*;

class Result {

    /*
     * Complete the 'findDay' function below.
     *
     * The function is expected to return a STRING.
     * The function accepts following parameters:
     *  1. INTEGER month
     *  2. INTEGER day
     *  3. INTEGER year
     */

    public static String findDay(int month, int day, int year) {
        Calendar cal = new GregorianCalendar(year, month-1, day); // month - 1 since month from 0
        System.out.print(year +":"+  month +":"+ day);        

        int weekDay = cal.get(Calendar.DAY_OF_WEEK);
        String dayWeek = "";
        switch(weekDay) {
            case 2:
            dayWeek = "MONDAY";
            break;
            case 3:
            dayWeek = "TUESDAY";
            break;
            case 4:
            dayWeek = "WEDNESDAY";
            break;
            case 5:
            dayWeek = "THURSDAY";
            break;
            case 6:
            dayWeek = "FRIDAY";
            break;
            case 7:
            dayWeek = "SATURDAY";
            break;
            case 1:
            dayWeek = "SUNDAY";
            break;
        }
        return dayWeek;
    }

}

public class UtilDayOfWeek {
    public static void main(String[] args) throws IOException {
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));

        String[] firstMultipleInput = bufferedReader.readLine().replaceAll("\\s+$", "").split(" ");

        int month = Integer.parseInt(firstMultipleInput[0]);

        int day = Integer.parseInt(firstMultipleInput[1]);

        int year = Integer.parseInt(firstMultipleInput[2]);

        String res = Result.findDay(month, day, year);
        System.out.println(res);
        bufferedReader.close();
        
    }
}