Java基础语言打印日历

import java.util.*;
    public class Demo{
        public static void main(String[] args){
            Scanner input=new Scanner(System.in);
            System.out.println("请输入年份");
            int year=input.nextInt();
            System.out.println("请输入月份");
            int month=input.nextInt();
            int allDays=0;
            for(int i=1990;i<year;i++){
                if((i % 4 ==0 && i % 100 != 0)  || (i % 400 == 0)){
                allDays += 366;
            }else{
                allDays += 365;
            }
        }
        int day = 0;
        for(int i = 1; i <= month ; i++){
            switch(i){
                case 1:
                case 3:
                case 5:
                case 7:
                case 8:
                case 10:
                case 12:
                    day = 31;
                    break;
                case 4:
                case 6:
                case 9:
                case 11:
                    day = 30;
                    break;
                case 2:
                    if((year % 4 ==0 && year % 100 != 0) || (year % 400 == 0)){
                        day = 29;
                    }else{
                        day = 28;
                    }
            }
            if(i < month){
                allDays += day;
               }
        }
        int week = (allDays+1) % 7;
        System.out.println("日\t一\t二\t三\t四\t五\t六");
        for(int i = 0; i < week; i++){
        System.out.print("\t");
         }
        for(int i = 1; i <= day ; i++){
            System.out.print(i+"\t");
            if((allDays + i) % 7 == 6)
                System.out.println();
            }
    }
  }