Thread: Homework - Calendar Assignment

Hi, I'm stuck on this project. This is the instructions:

CMPS 135 Programming Assignment 4

Problem:
Write a Java program to print out the calendar of any year provided that the day of January 1 of that year is known. (Note: Leap year is a year whose number is divisible by 4. The Feb. of a leap year has 29 days. You will receive extra points if you can print the calendar with 3 months in a row.)

Specification:
Use modular programming to write the program.





Currently, this is the code I have, but the program isn't working correctly:

import javax.swing.JOptionPane;
 
public class Assignment4Test
{
public static void display()
{ System.out.println(" S M T W T F S");
System.out.println("---------------------");
}
 
public static void main(String args[])
 
{ int year; 
String yearstr; 
int startday; 
String startdaystr; 
int month; 
int daysinmonth; 
String monthname; 
int spacesforstartday;
int date; 
 
yearstr = JOptionPane.showInputDialog("What is the number of the year?");
year = Integer.parseInt(yearstr);
 
startdaystr = JOptionPane.showInputDialog("What is the day of January 1? (S-1 M-2 T-3 W-4 T-5 F-6 S-7)");
startday = Integer.parseInt(startdaystr);
 
System.out.println(" "+year);
System.out.println(" ===="); 
 
for (month=1; month<=12; month++)
{
monthname="";
daysinmonth=0;
switch (month)
{
 
case 1:
 
monthname="Jan ";
daysinmonth=31;
break;
 
case 2:
 
monthname="Feb ";
if (year%4 == 0 && year%100 != 0 || year%400 == 0)
{ daysinmonth = 29; }
else
{ daysinmonth = 28; }
break;
 
case 3:
 
monthname = "March ";
daysinmonth = 31;
break;
 
case 4:
 
monthname="April ";
daysinmonth = 30;
break;
 
case 5:
 
monthname="May ";
daysinmonth = 31;
break;
 
case 6:
 
monthname="June ";
daysinmonth = 30;
break;
 
case 7:
 
monthname="July ";
daysinmonth = 31;
break;
 
case 8:
 
monthname="Aug ";
daysinmonth = 31;
break;
 
case 9:
 
monthname="Sept ";
daysinmonth = 30;
break;
 
case 10:
 
monthname="Oct ";
daysinmonth = 31;
break;
 
case 11:
 
monthname="Nov ";
daysinmonth = 30;
break;
 
case 12:
 
monthname="Dec ";
daysinmonth = 31;
break;
 
default:
 
System.out.println("Invalid data");
break;
 
}
 
System.out.println("");
System.out.println(" "+monthname);
System.out.println("");
 
display();
 
for(spacesforstartday=1;spacesforstartday<=startday;spacesforstartday++)
{System.out.print(" ");}
 
for(date=1; date<=daysinmonth; date++)
{ 
if(startday%7 == 0 && startday != 0)
{System.out.println();}
if(date<10)
{System.out.print(" "+date);}
else
{System.out.print(" "+date);}
startday=startday+1;
}
 
 
 
startday%=7;
System.out.println("");
System.out.println("");
}
 
 
 
System.exit(0);
 
}}

It's basically just supposed to print out a calendar, however for some reason the 1st of january always comes out one day early, which throws off the whole calendar.

Untitled.jpg
I uploaded a picture, the formatting was really messed up when copy/pasting it.

import javax.swing.JOptionPane;
 
public class Assignment4Test
{
  public static void display()
  { System.out.println("  S  M  T  W  T  F  S");
    System.out.println("---------------------");
  }
 
   public static void main(String args[])
 
  { int year;              
    String yearstr;        
    int startday;              
    String startdaystr;        
    int month;             
    int daysinmonth;             
    String monthname;          
    int spacesforstartday;
    int date;           
 
    yearstr = JOptionPane.showInputDialog("What is the number of the year?");
    year = Integer.parseInt(yearstr);
 
    startdaystr = JOptionPane.showInputDialog("What is the day of January 1? (S-1 M-2 T-3 W-4 T-5 F-6 S-7)");
    startday = Integer.parseInt(startdaystr);
 
    System.out.println("          "+year);
    System.out.println("          ====");      
 
    for (month=1; month<=12; month++)
    {
      monthname="";
      daysinmonth=0;
      switch (month)
      {
 
        case 1:
 
          monthname="Jan ";
          daysinmonth=31;
          break;
 
        case 2:
 
          monthname="Feb ";
          if (year%4 == 0 && year%100 != 0 || year%400 == 0)
          { daysinmonth = 29; }
          else
          { daysinmonth = 28; }
          break;
 
        case 3:
 
          monthname = "March ";
          daysinmonth = 31;
          break;
 
        case 4:
 
          monthname="April ";
          daysinmonth = 30;
          break;
 
        case 5:
 
          monthname="May ";
          daysinmonth = 31;
          break;
 
        case 6:
 
          monthname="June ";
          daysinmonth = 30;
          break;
 
        case 7:
 
          monthname="July ";
          daysinmonth = 31;
          break;
 
        case 8:
 
          monthname="Aug ";
          daysinmonth = 31;
          break;
 
        case 9:
 
          monthname="Sept ";
          daysinmonth = 30;
          break;
 
        case 10:
 
          monthname="Oct ";
          daysinmonth = 31;
          break;
 
        case 11:
 
          monthname="Nov ";
          daysinmonth = 30;
          break;
 
        case 12:
 
          monthname="Dec ";
          daysinmonth = 31;
          break;
 
        default:
 
          System.out.println("Invalid data");
          break;
 
      }
 
      System.out.println("");
      System.out.println("          "+monthname);
      System.out.println("");
 
      display();
 
      for(spacesforstartday=1;spacesforstartday<=startday;spacesforstartday++)
      {System.out.print("   ");}
 
      for(date=1; date<=daysinmonth; date++)
      { 
        if(startday%7 == 0 && startday != 0)
        {System.out.println();}
        if(date<10)
        {System.out.print("  "+date);}
        else
        {System.out.print(" "+date);}
        startday=startday+1;
      }
 
 
 
      startday%=7;
      System.out.println("");
      System.out.println("");
    }
 
 
 
    System.exit(0);
 
  }}

          2013
          ====
 
          Jan 
 
  S  M  T  W  T  F  S
---------------------
           1  2  3  4
  5  6  7  8  9 10 11
 12 13 14 15 16 17 18
 19 20 21 22 23 24 25
 26 27 28 29 30 31
 
 
          Feb 
 
  S  M  T  W  T  F  S
---------------------
                    1
  2  3  4  5  6  7  8
  9 10 11 12 13 14 15
 16 17 18 19 20 21 22
 23 24 25 26 27 28
 
 
          March 
 
  S  M  T  W  T  F  S
---------------------
                    1
  2  3  4  5  6  7  8
  9 10 11 12 13 14 15
 16 17 18 19 20 21 22
 23 24 25 26 27 28 29
 30 31
 
 
          April 
 
  S  M  T  W  T  F  S
---------------------
        1  2  3  4  5
  6  7  8  9 10 11 12
 13 14 15 16 17 18 19
 20 21 22 23 24 25 26
 27 28 29 30
 
 
          May 
 
  S  M  T  W  T  F  S
---------------------
              1  2  3
  4  5  6  7  8  9 10
 11 12 13 14 15 16 17
 18 19 20 21 22 23 24
 25 26 27 28 29 30 31
 
 
          June 
 
  S  M  T  W  T  F  S
---------------------
  1  2  3  4  5  6  7
  8  9 10 11 12 13 14
 15 16 17 18 19 20 21
 22 23 24 25 26 27 28
 29 30
 
 
          July 
 
  S  M  T  W  T  F  S
---------------------
        1  2  3  4  5
  6  7  8  9 10 11 12
 13 14 15 16 17 18 19
 20 21 22 23 24 25 26
 27 28 29 30 31
 
 
          Aug 
 
  S  M  T  W  T  F  S
---------------------
                 1  2
  3  4  5  6  7  8  9
 10 11 12 13 14 15 16
 17 18 19 20 21 22 23
 24 25 26 27 28 29 30
 31
 
 
          Sept 
 
  S  M  T  W  T  F  S
---------------------
     1  2  3  4  5  6
  7  8  9 10 11 12 13
 14 15 16 17 18 19 20
 21 22 23 24 25 26 27
 28 29 30
 
 
          Oct 
 
  S  M  T  W  T  F  S
---------------------
           1  2  3  4
  5  6  7  8  9 10 11
 12 13 14 15 16 17 18
 19 20 21 22 23 24 25
 26 27 28 29 30 31
 
 
          Nov 
 
  S  M  T  W  T  F  S
---------------------
                    1
  2  3  4  5  6  7  8
  9 10 11 12 13 14 15
 16 17 18 19 20 21 22
 23 24 25 26 27 28 29
 30
 
 
          Dec 
 
  S  M  T  W  T  F  S
---------------------
     1  2  3  4  5  6
  7  8  9 10 11 12 13
 14 15 16 17 18 19 20
 21 22 23 24 25 26 27
 28 29 30 31

January 1st of this year lands on a Tuesday, yet the program assigns it to Wednesday and it throws off the whole calendar.

This code gets the variable that assigns the day of the first of January

    startdaystr = JOptionPane.showInputDialog("What is the day of January 1? (S-1 M-2 T-3 W-4 T-5 F-6 S-7)");
    startday = Integer.parseInt(startdaystr);

This code handles the spacing and the first of the month.

for(spacesforstartday=1;spacesforstartday<=startday;spacesforstartday++)
      {System.out.print("   ");}
 
      for(date=1; date<=daysinmonth; date++)
      { 
        if(startday%7 == 0 && startday != 0)
        {System.out.println();}
        if(date<10)
        {System.out.print("  "+date);}
        else
        {System.out.print(" "+date);}
        startday=startday+1;
      }
 
 
 
      startday%=7;
      System.out.println("");
      System.out.println("");
    }

I've messed with the code for quite a while, I can't seem to get it to work correctly without pushing all of the other dates onto a new line.

The first two variables that you mentioned were necessary, when I altered them the problem worsened.

Nothing that I'm trying is helping to correct the issue. Do you have any suggested fixed?