关于日期的java小程序，写的比较粗糙

//2013-10-7
import java.util.*;
import java.text.DateFormatSymbols;
public class dateprint{
    public static void main(String[] args){
        int year,month,day;
        String input;
        Scanner in=new Scanner(System.in);
        input=in.nextLine();
        year=Integer.parseInt(input.substring(0,4));
        month=Integer.parseInt(input.substring(5,7));
        day=Integer.parseInt(input.substring(8));
        PRINT a=new PRINT();
        a.Monthprint(year,month,day);
            
    }
}

class PRINT{
    public void Monthprint(int y,int m,int D){
        GregorianCalendar d=new GregorianCalendar(y,m,D);

        int today=d.get(Calendar.DAY_OF_MONTH);
        int month=d.get(Calendar.MONTH);

        d.set(Calendar.DAY_OF_MONTH,1);        //将d设为该月的第一天

        int weekday=d.get(Calendar.DAY_OF_WEEK);   //得到d是星期几
        int firstdayofweek=d.getFirstDayOfWeek();

        int indent=0;                //判断第一周前面有几个空
        while(weekday!=firstdayofweek){
            indent++;
            d.add(Calendar.DAY_OF_WEEK,-1);
            weekday=d.get(Calendar.DAY_OF_WEEK);
        }

        //打印weekday names
        String[] weekdayname=new DateFormatSymbols().getShortWeekdays();
        do{
            System.out.printf("%4s",weekdayname[weekday]);
            d.add(Calendar.DAY_OF_MONTH,1);
            weekday=d.get(Calendar.DAY_OF_WEEK);
        }while(weekday!=firstdayofweek);

        System.out.println();

        for(int i=1;i<=indent;i++)
          System.out.print("    ");
        d.set(Calendar.DAY_OF_MONTH,1);

        do{
            int day=d.get(Calendar.DAY_OF_MONTH);
            System.out.printf("%3d",day);

            if(day==today) System.out.print("*");
            else System.out.print(" ");

            d.add(Calendar.DAY_OF_MONTH,1);
            weekday=d.get(Calendar.DAY_OF_WEEK);

            if(weekday==firstdayofweek) System.out.println();
        }while(d.get(Calendar.MONTH)==month);

        if(weekday!=firstdayofweek) System.out.println();
        
    }
}