Exercise_06_34 Answer!

Hey man,

I could not find your answer to Programming Exercise Chapter. 6 Number 34. so I thought I could share my answer 😃. PS: Don’t know it’s efficient, or even a good implementation, but it works pretty good, for any given year. PS2: I could not find the answer to question No. 33 too, and unfortunately I couldn’t solve it yet, though I am working hard on it. When I have written the answer, I will share the code. 😃

import java.util.Scanner;

/**
 * Created by SquirrelCoder on 29-Jan-17.
 */
public class ZellerAlgorithm {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);

        // getting user input
        System.out.print("Enter full year (e.g., 2012): ");
        int year = input.nextInt();
        System.out.print("Enter month as number between 1 and 12: ");
        int month = input.nextInt();

        // check user input
        if (!checkMonth(month)) {
            System.exit(0);
        }

        // print the calendar header
        printCalendarHeader(month, year);

        // print the calendar first day
        printFirstDay(month, year);

        // print the calendar itself
        printCalendarItself(month, year);

    }

    public static int weekDay(int day, int month, int year) {
        if (month == 1 || month == 2) {
            month = month + 12;
            year--;
        }
        int q, m, k, j, h;
        q = day;
        m = month;
        k = year % 100;
        j = (int) (year / 100.0);
        h = (q + (int) ((13 * (m + 1)) / 5.0) + k + (int) (k / 4.0) + (int) (j / 4.0) + (5 * j)) % 7;
        return h;
    }

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

    public static void printCalendarHeader(int month, int year) {
        switch (month) {
            case 1:
                System.out.print("\t\tJanuary\t");
                System.out.println(year);
                System.out.println("---------------------------");
                break;
            case 2:
                System.out.print("\t\tFebruary\t");
                System.out.println(year);
                System.out.println("---------------------------");
                break;
            case 3:
                System.out.print("\t\tMarch\t");
                System.out.println(year);
                System.out.println("---------------------------");
                break;
            case 4:
                System.out.print("\t\tApril\t");
                System.out.println(year);
                System.out.println("---------------------------");
                break;
            case 5:
                System.out.print("\t\tMay\t");
                System.out.println(year);
                System.out.println("---------------------------");
                break;
            case 6:
                System.out.print("\t\tJune\t");
                System.out.println(year);
                System.out.println("---------------------------");
                break;
            case 7:
                System.out.print("\t\tJuly\t");
                System.out.println(year);
                System.out.println("---------------------------");
                break;
            case 8:
                System.out.print("\t\tAugust\t");
                System.out.println(year);
                System.out.println("---------------------------");

                break;
            case 9:
                System.out.print("\t\tSeptember\t");
                System.out.println(year);
                System.out.println("---------------------------");
                break;
            case 10:
                System.out.print("\t\tOctober\t");
                System.out.println(year);
                System.out.println("---------------------------");
                break;
            case 11:
                System.out.print("\t\tNovember\t");
                System.out.println(year);
                System.out.println("---------------------------");
                break;
            case 12:
                System.out.print("\t\tDecember\t");
                System.out.println(year);
                System.out.println("---------------------------");
                break;


        }
        System.out.println("Sun\tMon\tTue\tWed\tThu\tFri\tSat");
    }

    public static int lastDayOfMonth(int month, int year) {
        int lastDayOfMonth;
        if (month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10 || month == 12) {
            lastDayOfMonth = 31;
        } else if (month == 2) {
            if (isLeapYear(year)) {
                lastDayOfMonth = 29;
            } else {
                lastDayOfMonth = 28;
            }
        } else {
            lastDayOfMonth = 30;
        }
        return lastDayOfMonth;
    }

    public static boolean checkMonth(int month) {
        if (month > 12 || month < 0) {
            System.out.println("Invalid Month!");
            return false;
        }
        return true;
    }

    public static void printFirstDay(int month, int year) {
        int firstDay = weekDay(1, month, year);
        switch (firstDay) {
            case 0:
                System.out.print("\t\t\t\t\t\t1");
                break;
            case 1:
                System.out.print("1");
                break;
            case 2:
                System.out.print("\t1");
                break;
            case 3:
                System.out.print("\t\t1");
                break;
            case 4:
                System.out.print("\t\t\t1");
                break;
            case 5:
                System.out.print("\t\t\t\t1");
                break;
            case 6:
                System.out.print("\t\t\t\t\t1");
                break;

        }
        System.out.print("\t");
    }

    public static void printCalendarItself(int month, int year) {

        // find out the last day of that month
        // whether it's 28/29/30/31 days
        int lastDayOfMonth = lastDayOfMonth(month, year);

        // print the calendar itself
        for (int i = 2; i <= lastDayOfMonth; i++) {
            int printedDay = weekDay(i, month, year);
            if (printedDay == 1) {
                System.out.println();
            }
            System.out.print(i + "\t");
        }
    }
}

[SleekPanther]

@SquirrelCoder I was inspired and ended up making all the edits I mentioned (plus a few more). I was wrong in some of my earlier comments, but you can see the final version in a pull request or check out my actual commit I made some structural edits (mostly which method comes first is kind of subjective) and I renamed some variables/methods to what I personally think is more helpful

[jsquared21]

Kool im glad i asked you cause, forking, cloning, pulling and pushing, that is what github is all about. SleekPanther defined the concept well. You should try and learn these concepts and practice them while learning java and working in github. Like SleekPanter said it can be confusing in the beginning but learning them will pay off big time.