万年历的编写（java）

import java.util.Scanner;
public class CalendarDemo{
public static void main(String []args){
int year;
int month;
int days=0;
int sumdays=0;
boolean isRn;
System.out.println("************万年历查询*************");
Scanner input=new Scanner(System.in);
System.out.println("请输入年份：");
year=input.nextInt();
System.out.println("请输入月份");
month=input.nextInt();
if((year%400==0)||(year%4==0&&year%100!=0)){
isRn=true;
System.out.println(year+"是润年");
}
else{
isRn=false;
System.out.println(year+"不是润年");
}
//计算总的天数
for(int i=1900;i<year;++i){
if(i%400==0||(i%4==0&&i%100!=0)){
sumdays+=366;
}
else{
sumdays+=365;
}
}
for(int j=1;j<=month;j++){
switch(j){
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
days=31;
break;
case 2:
if(isRn){
days=29;
}else{
days=28;
}
break;
case 4:
case 6:
case 9:
case 11:
days=30;
break;
}
if(month!=j){
sumdays+=days;
}
}
//求出星期几
int beforedays;
beforedays=1+sumdays%7;
//星期天第一列前面不需要制表符；
if(beforedays==7){
beforedays=0;
}
System.out.println("星期天\t星期一\t星期二\t星期三\t星期四\t星期五\t星期六");
for(int i=0;i<beforedays;++i){
System.out.print("\t");
}
for(int j=1;j<=days;++j){
System.out.print(j+"\t");
if((j+beforedays)%7==0){
System.out.println();
}
}
}
}