Help needed

I'm writing a class to output month and day using JOptionpane. my problem is that i cannot invoke the right code from calendar.java to complete the class... I'll show you how far i got by pasting the codes. if the calendar class is also needed let me know to insert it.

import javax.swing.JOptionPane;

public class OptionalLab {

/** Main method */
public static void main(String[] args) {

String output = "";


// Prompt the user to enter year
String yearString = JOptionPane.showInputDialog(null,
"Enter full year (i.e. 2001):",
"Enter Year", JOptionPane.QUESTION_MESSAGE);

Integer.parseInt(yearString);

// Prompt the user to enter month
String monthString = JOptionPane.showInputDialog(null,
"Enter month in number between 1 and 12:",
"Enter Month", JOptionPane.QUESTION_MESSAGE);

Integer.parseInt(monthString);

// invoke method here

JOptionPane.showMessageDialog(null, output);

}
}

you know
here is the calendar class
public class Calendar {
/** Print the calendar for a month in a year */
private String output = new String();


public String getOutput(){
return output;
}

Calendar(int year, int month){
printMonth(year, month);
}

private void printMonth(int year, int month) {
// Get start day of the week for the first date in the month
int startDay = getStartDay(year, month);

// Get number of days in the month
int numOfDaysInMonth = getNumOfDaysInMonth(year, month);

// Print headings
printMonthTitle(year, month);

// Print body
printMonthBody(startDay, numOfDaysInMonth);
}

/** Get the start day of the first day in a month */
private int getStartDay(int year, int month) {
// Get total number of days since 1/1/1800
int startDay1800 = 3;
long totalNumOfDays = getTotalNumOfDays(year, month);

// Return the start day
return (int)((totalNumOfDays + startDay1800) % 7);
}

/** Get the total number of days since Jan 1, 1800 */
private long getTotalNumOfDays(int year, int month) {
long total = 0;

// Get the total days from 1800 to year -1
for (int i = 1800; i < year; i++)
if (isLeapYear(i))
total = total + 366;
else
total = total + 365;

// Add days from Jan to the month prior to the calendar month
for (int i = 1; i < month; i++)
total = total + getNumOfDaysInMonth(year, i);

return total;
}

/** Get the number of days in a month */
private int getNumOfDaysInMonth(int year, int month) {
if (month == 1 || month==3 || month == 5 || month == 7 ||
month == 8 || month == 10 || month == 12)
return 31;

if (month == 4 || month == 6 || month == 9 || month == 11)
return 30;

if (month == 2)
if (isLeapYear(year))
return 29;
else
return 28;

return 0; // If month is incorrect.
}

/** Determine if it is a leap year */
private boolean isLeapYear(int year) {
if ((year % 400 == 0) || ((year % 4 == 0) && (year % 100 != 0)))
return true;

return false;
}

/** Print month body */
private void printMonthBody(int startDay, int numOfDaysInMonth) {
// Pad space before the first day of the month
int i = 0;
for (i = 0; i < startDay; i++)
output += " ";

for (i = 1; i <= numOfDaysInMonth; i++) {
if (i < 10)
output += " " + i;
else
output += " " + i;

if ((i + startDay) % 7 == 0)
output += "\n";
}

output += "\n";
}

/** Print the month title, i.e. May, 1999 */
private void printMonthTitle(int year, int month) {
output += " " + getMonthName(month)
+ ", " + year + "\n";
output += "-----------------------------------------------\n";
output += " Sun Mon Tue Wed Thu Fri Sat\n";
}

/** Get the English name for the month */
String getMonthName(int month) {
String monthName = null;
switch (month) {
case 1: monthName = "January"; break;
case 2: monthName = "February"; break;
case 3: monthName = "March"; break;
case 4: monthName = "April"; break;
case 5: monthName = "May"; break;
case 6: monthName = "June"; break;
case 7: monthName = "July"; break;
case 8: monthName = "August"; break;
case 9: monthName = "September"; break;
case 10: monthName = "October"; break;
case 11: monthName = "November"; break;
case 12: monthName = "December";
}

return monthName;
}
}

Do you have a specific question that is related to some part of this code?

I need to add a few lines of codes on the optional class to invoke methods from the calendar class, so that i can have and output for the days of any month.. I just need some help to get started.. can you help me?

You will need a Calendar object in the main method. Do you know how to create an object of a class?

In this case no because the constructors are private.. and it's my first time dealing with JOptionpane. I'm confused!

Is there any special reason why all your Calendar methods are private?

The calendar class was provided to me.. i have to come up with the optional class, which includes invoking methods from Calendar class.