How to write a program for calendar in Java

calendar for a given month of a given year, or of the current month and year.

import java.util.*;
import java.text.*;
/** Print a month page.
* Only works for the Western calendar.
*/
public class CalendarPage {
/** The names of the months */
String[] months = {
"January", "February", "March", "April",
"May", "June", "July", "August",
"September", "October", "November", "December"
};
/** The days in each month. */
public final static int dom[] = {
31, 28, 31, 30, /* jan feb mar apr */
31, 30, 31, 31, /* may jun jul aug */
30, 31, 30, 31 /* sep oct nov dec */
};
/** Compute which days to put where, in the Cal panel */
public void print(int mm, int yy) {
/** The number of days to leave blank at the start of this
month */
int leadGap = 0;
System.out.print(months[mm]); // print month and year

System.out.print(" ");
System.out.print(yy);
System.out.println( );
if (mm < 0 || mm > 11)
throw new IllegalArgumentException("Month " + mm + " bad,
must be 0-11");
GregorianCalendar calendar = new GregorianCalendar(yy, mm, 1);
System.out.println("Su Mo Tu We Th Fr Sa");
// Compute how much to leave before the first.
// getDay( ) returns 0 for Sunday, which is just right.
leadGap = calendar.get(Calendar.DAY_OF_WEEK)-1;
int daysInMonth = dom[mm];
if (calendar.isLeapYear(calendar.get(Calendar.YEAR)) && mm ==
1)
++daysInMonth;
// Blank out the labels before 1st day of month
for (int i = 0; i < leadGap; i++) {
System.out.print(" ");
}
// Fill in numbers for the day of month.
for (int i = 1; i <= daysInMonth; i++) {
// This "if" statement is simpler than fiddling with
NumberFormat
if (i<=9)
System.out.print(' ');
System.out.print(i);
if ((leadGap + i) % 7 == 0) // wrap if end of line.
System.out.println( );
else
System.out.print(' ');
}
System.out.println( );
}
/** For testing, a main program */
public static void main(String[] av) {
int month, year;
CalendarPage cp = new CalendarPage( );
// print the current month.
if (av.length == 2) {
cp.print(Integer.parseInt(av[0])-1,
Integer.parseInt(av[1]));
} else {
Calendar c = Calendar.getInstance( );
cp.print(c.get(Calendar.MONTH), c.get(Calendar.YEAR));
}
}
}