用java write calendar

import java.util.Scanner;
 
public class Test {
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		System.out.print("请输入年份：");
		int year = in.nextInt();
		System.out.print("请输入月份：");
		int month = in.nextInt();
		int days = 1;
		if (month == 2) {
			if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) {
				days = 29;
			} else {
				days = 28;
			}
		}
		if (month == 4 || month == 6 || month == 9 || month == 11) {
			days = 30;
		} else {
			days = 31;
		}
 
		int sum = 0;
 
		for (int i = 1900; 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 wekday = sum % 7;
		System.out.println("日\t一\t二\t三\t四\t五\t六");
		for (int i = 1; i <= wekday; i++) {
			System.out.print("\t");
		}
 
		for (int i = 1; i <= days; i++) {
			if (sum % 7 == 6) {
				System.out.print(i + "\n");
			} else {
				System.out.print(i + "\t");
 
			}
			sum++;
		}
	}
}