Monthly Calender Program in Java

Introduction

• In this blog, I am going to explain about the monthly calendar program in Java

Software Requirements

• Java, Notepad.

Program

import java.util.*;
import java.text.*;

public class MonthCalender {

    public final static String[] monthcalender = {
        "January", "February", "March", "April", "May", "June", "July",
            "August", "September", "October", "November", "December"};

        public final static int daysinmonths[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

        private void displayMonth(int month, int year) {

            // The number of days to leave blank at
            // the start of this month.

            int blankdays = 0;
            System.out.println("  " + monthcalender[month] + " " + year);

            if (month < 0 || month > 11) {
                throw new IllegalArgumentException(
                    "Month " + month + " is not valid and must lie in between 0 and 11");
            }

            GregorianCalendar cldr = new GregorianCalendar(year, month, 1);
            System.out.println("Sunday Monday Tuesday Wednesday Thursday Friday Saturday");

            // Compute how much to leave before before the first day of the month.
            // getDay() returns 0 for Sunday.

            blankdays = cldr.get(Calendar.DAY_OF_WEEK)-1;
            int daysInMonth = daysinmonths[month];

            if (cldr.isLeapYear(cldr.get(Calendar.YEAR)) && month == 1) {

                ++daysInMonth;
            }

            // Blank out the labels before 1st day of the month
            for (int i = 0; i < blankdays; i++) {
                System.out.print("   ");
            }

            for (int i = 1; i <= daysInMonth; i++) {

                // This "if" statement is simpler than messing with NumberFormat
                if (i<=9) {
                    System.out.print(" ");
                }
                System.out.print(i);

                if ((blankdays + i) % 7 == 0) { // Wrap if EOL
                System.out.println();
                }
                else {
                    System.out.print(" ");
                }
            }
        }

    /**
     * Sole entry point to the class and application.
     * @param args Array of String arguments.
     */
    public static void main(String[] args) {

        int mon, yr;
        MonthCalender moncldr = new MonthCalender();

        if (args.length == 2) {
            moncldr.displayMonth(Integer.parseInt(args[0])-1, Integer.parseInt(args[1]));
        }
        else {
            Calendar todaycldr = Calendar.getInstance();
            moncldr.displayMonth(todaycldr.get(Calendar.MONTH), todaycldr.get(Calendar.YEAR));
        }
    }
}

Output