java 实现一个简单的万年历

package zuoye;

import java.util.Scanner;

public class WanNianLi {
	public static void main(String[] args) {
		System.out.println("欢迎使用小鸟万历");
		Scanner scanner = new Scanner(System.in);
		System.out.println("请输入要查询的年份：");
		int year = scanner.nextInt();
		System.out.println("请输入要查询的月份：");
		int month = scanner.nextInt();
		System.out.println("\t" + "\t" + "\t" + year + "年" + month + "月");
		System.out.println("--------------------------------------------------------");
		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");
		boolean run = false;
		if ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0)) {
			run = true; //  判断是否闰年
		}
		int sumDay = 0;// 设置距离天数变量
		for (int i = 1900; i < year; i++) {
			if ((i % 4 == 0 && i % 100 != 0) || (i % 400 == 0)) {
				sumDay += 366;
			} else {              // 计算闰年和不是闰年的总天数
				sumDay += 365;
			}
		}
		int day = 0; // 设置每月的天数变量
		int beforeDay = 0; // 设置一个查询年份月份之前的天数的变量
		for (int j = 1; j <= month; j++) {
			switch (j) {
			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 (run) {
					day = 29;
				} else {
					day = 28;
				}
				break;
			default:
				System.out.println("月份输入有误");
				break;
			}
			if (j < month) {
				beforeDay = beforeDay + day;  //把查询月份之前的月份的天数全部加起来
			}
		}
		sumDay = sumDay + beforeDay;  // 算到总天数里
		int firstDay = 0;   //设置月份第一天的变量
		int a = 1 + sumDay % 7; // 1900年1月1日是星期一  总天数对7取余加1得到星期几    星期日为0 (也就是7)
		if (a == 7) {
			firstDay = 0;
		} else {
			firstDay = a;
		}
		for (int b = 0; b < firstDay; b++) {
			if(firstDay != 0) {
				System.out.print("\t"); //  第一行的空格 
			}
			 
		}
		for (int c = 1; c <= day; c++) {
			System.out.print(c + "\t");   // 日期
			if ((sumDay + c) % 7 == 6) {
				System.out.print("\n");  //  因为星期六要拐行
			}
		}

	}
}