编写万年历：输入一个年份，再输入一个月份，把那个月的日历打印出来(1900年1月1日是星期一)

 1 public static void main(String[] args) {
 2         Scanner in = new Scanner(System.in);
 3         //输入年份
 4         System.out.println("请输入年份(1900之后的)：");
 5         int year = in.nextInt();
 6         //输入月份
 7         System.out.println("请输入月份：");
 8         int month = in.nextInt();
 9         //判断数据输入是否有误
10         if (year < 1900 || month >12 || month < 1){
11             System.out.println("对不起，你输入的数据有误！");
12             return;
13         }
14         //获取1900年到输入年份的总天数
15         int allDayOfYear = getAllDayOfYear(1900,year);
16 
17         //获取输入年份从1月到输入月份的总天数
18         int allDayOfMonth = getAllDayOfMonth(year,1,month);
19 
20         //获得总天数
21         int allDay = allDayOfYear + allDayOfMonth;
22         //打印日期
23         printCalendar(allDay,getDayOfMonth(year,month));
24 
25     }

public static int getAllDayOfYear(int startYear,int endYear){
        //定义年的总天数
        int allDayOfYear = 0;
        for (int i = startYear; i < endYear; i++) {
            if (judgeLeapYear(i)){
                allDayOfYear += 366;
            }else {
                allDayOfYear +=365;
            }
        }
        return allDayOfYear;

    }

1 public static int getAllDayOfMonth(int year,int startMonth,int endMonth){
2         int allDayOfMonth = 0;
3         for (int i = startMonth; i < endMonth; i++) {
4             allDayOfMonth += getDayOfMonth(year,i);
5         }
6         return allDayOfMonth;
7     }

 1 public static int getDayOfMonth(int year,int month){
 2         //定义月的天数
 3         int day = 0;
 4         switch (month){
 5             case 1:
 6             case 3:
 7             case 5:
 8             case 7:
 9             case 8:
10             case 10:
11             case 12:
12                 day = 31;
13                 break;
14             case 4:
15             case 6:
16             case 9:
17             case 11:
18                 day = 30;
19                 break;
20             case 2:
21                 if (judgeLeapYear(year)){
22                     day = 29;
23                 }else {
24                     day = 28;
25                 }
26                 break;
27         }
28         return day;
29     }

1 public static boolean judgeLeapYear(int year){
2         if (year % 4 == 0 && year % 100 !=0 || year % 400 == 0){
3             return true;
4         }
5         return false;
6     }

 1 public static void printCalendar(int allDay,int day){
 2         //打印开头的信息
 3         System.out.println("星期日\t星期一\t星期二\t星期三\t星期四\t星期五\t星期六");
 4         //换行变量
 5         int num = 0;
 6         //计算输入的月份1号是星期几
 7         int week = allDay % 7 +1;
 8         for (int i = 0; i < week; i++) {
 9             System.out.print("\t\t");
10             num++;
11         }
12         //打印日期
13         for (int i = 1; i <= day; i++) {
14             //判断
15             if (num %7 == 0){
16                 System.out.println();
17             }
18             System.out.print(i+"\t\t");
19             num++;
20         }
21     }