DaysInMonth.java

public class DaysInMonth {
    public static void main(String[] args) {
        int month = 2, year = 2024;
        System.out.println("Days in month " + month + " of " + year + " = " + daysInMonth(month, year));
    }

    static int daysInMonth(int month, int year) {
        switch (month) {
            case 1: case 3: case 5: case 7: case 8: case 10: case 12:
                return 31;
            case 4: case 6: case 9: case 11:
                return 30;
            case 2:
                return isLeapYear(year) ? 29 : 28;
            default:
                throw new IllegalArgumentException("Invalid month: " + month);
        }
    }

    static boolean isLeapYear(int year) {
        return (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0);
    }
}