把过程贴上来好了~~~

package ghf;
import javax.swing.JOptionPane;
public class PrintCalendar {
public static void main(String[] args) {
// TODO Auto-generated method stub
String numberString=JOptionPane.showInputDialog("Enter a year");
int number=Integer.parseInt(numberString);
int year=number;
String number2String=JOptionPane.showInputDialog("enter month as number between 1 and 12");
int number2=Integer.parseInt(number2String);
int month=number2;
printMonth(year,month);}
public static void printMonth(int year,int month){
printMonthTitle( year, month);
printMonthBody( year,month);}
public static void printMonthTitle(int year,int month){
JOptionPane.showMessageDialog(null," "+getMonthName(month)+" "+year+"------------"+"Sun Mon Tue Wed Thu Fri Sat");
}
public static String getMonthName(int month){
String monthName=" ";
switch(month){
case 1:monthName="January";break;
case 2:monthName="Febuary";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;}
public static void printMonthBody(int year,int month){
int startDay=getStartDay(year,month);
int numberOfDaysInMonth=getNumberOfDaysInMonth(year,month);
int i=0;
for(i=0;i<startDay;i++)
System.out.print(" ");
for(i=1;i<=numberOfDaysInMonth;i++){
System.out.printf("%4d", i);
if((i+startDay)%7==0)
System.out.println();}
System.out.println();}
public static int getStartDay(int year,int month){
final int START_DAY_FOR_JAN_1_1800=3;
int totalNumberOfDays=getTotalNumberOfDays(year,month);
return(totalNumberOfDays+START_DAY_FOR_JAN_1_1800)%7;}
public static int getTotalNumberOfDays(int year,int month){
int total=0;
for(int i=1800;i<year;i++)
if(isLeapYear(i))
total=total+366;
else
total=total+365;
for(int i=1;i<month;i++)
total=total+getNumberOfDaysInMonth(year,i);
return total;}
public static int getNumberOfDaysInMonth(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) return 28;
return 0;}
public static boolean isLeapYear(int year){
return year % 400==0||(year%4==0&&year%100!=0);
}
}

附赠一张女神图片~~帮帮忙嘛~大一新生的作业= = = ！！