public static String findDay(int month, int day, int year) {

    LocalDate date = LocalDate.of(year, month, day);

    DayOfWeek dayOfWeek = date.getDayOfWeek();
    String dayOfWeekName = dayOfWeek.getDisplayName(TextStyle.FULL, Locale.ENGLISH);

    return dayOfWeekName.toUpperCase();

}

Easy Solution

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 calendar = Calendar.getInstance();

    calendar.set(year,month-1,day);

    System.out.println(calendar.getTime());

    int res = calendar.get(calendar.DAY_OF_WEEK);

    switch (res) {
        case 1 -> {return "SUNDAY";}
        case 2 -> {return "MONDAY";}
        case 3 -> {return "TUESDAY";}
        case 4 -> {return "WEDNESDAY";}
        case 5 -> {return "THURSDAY";}
        case 6 -> {return "FRIDAY";}
        case 7 -> {return "SATURDAY";}
        default -> {return "nachobc";}
    }

}

}

my answer by pass All testcase

public static String findDay(int month, int day, int year) { Calendar calendar = Calendar.getInstance(); calendar.set(year, month - 1, day); int dayOfWeek = calendar.get(Calendar.DAY_OF_WEEK); System.out.println(dayOfWeek); String[] dayOf = { "SUNDAY", "MONDAY",
"TUESDAY", "WEDNESDAY", "THURSDAY", "FRIDAY", "SATURDAY" }; return dayOf[dayOfWeek - 1]; } }

//Using Zeller's Congruence Formula

import java.io.; import java.math.; import java.security.; import java.text.; import java.util.; import java.util.concurrent.; import java.util.function.; import java.util.regex.; import java.util.stream.; import static java.util.stream.Collectors.joining; import static java.util.stream.Collectors.toList; import java.time.;

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) {
    if(month<3){
     month+=12;
     year-=1;   
    }
    int years=year%100;
    int cyears=year/100;
    //int h=(day+(13*(month+1))/5+years+(years/4)+(cyears/4)-2*cyears)%7;
    int h = (day + (13 * (month + 1)) / 5 + years + (years / 4) + (cyears / 4) - 2 * cyears) % 7;
    if (h < 0) {
    h += 7;  // Ensure h is a positive number between 0 and 6
}
    String[] weekday={"SATURDAY","SUNDAY","MONDAY","TUEDAY","WEDNESDAY","THURSDAY","FRIDAY"};
return weekday[h];
}

}

public class Solution { public static void main(String[] args) throws IOException { BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in)); BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH")));

    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);

    bufferedWriter.write(res);
    bufferedWriter.newLine();

    bufferedReader.close();
    bufferedWriter.close();
}

}