需求：

1. 输出界面上要求能以一定的格式化形式展示出来,有年、月、星期的信息和字样
2. 要求针对不同的子功能设计函数完成,函数数量不得少于3个
3. 要求能循环执行,直到用户输入q"时退出

实现：

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.*;

public class RiLi {

    public static void main(String[] args) throws ParseException {
        Scanner sc = new Scanner(System.in);

        while (true) {
            System.out.println("---查询日历选项---");
            System.out.println("1.查询一年日历:例如2021");
            System.out.println("2.查询单月日历:例如2021 06");
            System.out.println("输入选项:");
            String choice = sc.nextLine();
            switch (choice) {
                case "1":
                    System.out.println("-查询一年日历-");
                    System.out.println("输入查询年份:");
                    String year = sc.nextLine();
                    myyear(year);
                    break;
                case "2":
                    System.out.println("-查询单月日历-");
                    System.out.println("输入查询年份:");
                    String year_solo = sc.nextLine();
                    System.out.println("输入查询月份:");
                    String month_solo = sc.nextLine();
                    myyear(year_solo,month_solo);
                    break;
                case "q":
                    System.out.println("-退出程序-");
                    System.exit(0);
            }
        }

    }
//    查询一年的日历
    public static void myyear(String year) throws ParseException {
        for (int mouth = 1; mouth <=12 ; mouth++) {
            System.out.println(mouth + "月 日历:");

            int firstDay = 0;
            int endDay = 0;

            String str = year + "-" + mouth;
            DateFormat format = new SimpleDateFormat("yyyy-MM");
            Date date = format.parse(str);

            Calendar c = new GregorianCalendar();
            c.setTime(date);
            endDay = c.getActualMaximum(Calendar.DATE);
            c.set(Calendar.DATE, 1);
            firstDay = c.get(Calendar.DAY_OF_WEEK);

            System.out.println("------------------------------------------------------");
            System.out.println("周日 周一 周二 周三 周四 周五 周六");
            System.out.println("------------------------------------------------------");
            for (int j = 1; j < firstDay; j++)
            {
                System.out.print("\t");
            }
            for (int i = 1; i <= endDay; i++)
            {
                System.out.print(i + "\t");
                if ((i - (8 - firstDay)) % 7 == 0)
                {
                    System.out.println("\n");
                }
            }
            System.out.println();
        }

    }
//  查询单月日历
    public static void myyear(String year, String month) throws ParseException {
        System.out.println(year+"年-"+month+"月 日历:");

        int firstDay = 0;
        int endDay = 0;

        String str = year + "-" + month;

        DateFormat format = new SimpleDateFormat("yyyy-MM");
        Date date = format.parse(str);

        Calendar c = new GregorianCalendar();
        c.setTime(date);
        endDay = c.getActualMaximum(Calendar.DATE);
        c.set(Calendar.DATE, 1);
        firstDay = c.get(Calendar.DAY_OF_WEEK);

        System.out.println("------------------------------------------------------");
        System.out.println("周日 周一 周二 周三 周四 周五 周六");
        System.out.println("------------------------------------------------------");
        for (int j = 1; j < firstDay; j++)
        {
            System.out.print("\t");
        }
        for (int i = 1; i <= endDay; i++)
        {
            System.out.print(i + "\t");
            if ((i - (8 - firstDay)) % 7 == 0)
            {
                System.out.println("\n");
            }
        }
    }

}