用java写一个万年历

import java.util.Scanner;
public class rili {
    static boolean mark=true;
    public static void main(String[] args){
        Scanner in=new Scanner(System.in);
        Scanner in1=new Scanner(System.in);
        while(rili.mark){
        System.out.println("请输入年份");
        int year=in.nextInt();
        System.out.println("请输入月份");
        int month=in.nextInt();
        int sum=0;
        int c;
        for(int i=1990;i<year;i++){
            if(i%4==0&&i%100!=0||i%400==0){
                sum+=366;
            }else {
                sum+=365;
        }
        }
        for(int i=1;i<month;i++){
            if(i==2){
                if(year%4==0&&year%100!=0||year%400==0){
                    sum+=29;
                }else{
                    sum+=28;
                }
            }else{
                if(i==4||i==6||i==9||i==11){
                sum+=30;
                }else{
                    sum+=31;
                }
            }
        }
        sum+=1;
        int weekday=sum%7;
        System.out.println("日\t一\t二\t三\t四\t五\t六");
        for(int i=1;i<=weekday;i++){
            System.out.print("\t");}

        if(month==2){
                if(year%4==0&&year%100!=0||year%400==0){c=29;}
                else{c=28;}}
                else{if(month==4||month==6||month==9||month==11){c=30;}
                    else{c=31;}}

            for(int i = 1;i<=c;i++){
                if(sum%7==6){
                    System.out.print(i+"\n");}
                else{
                    System.out.print(i+"\t");}
                sum++;  }

        System.out.println("\n");
        System.out.println("如果想继续请按1，退出按2");
        int flag=in1.nextInt();
        if(flag==2)
            mark=false;

}
}
}