如何实现万年历上一月、下一月、上一年、下一年的查询。

我现在的代码已经可以输出一个月的日历了，但是现在想要一直能输入年份、月份然后输出此年月的日历，这个要怎么实现呢？

Java中可以使用java.util.Calendar和java.text.SimpleDateFormat类来实现万年历上一月、下一月、上一年、下一年的查询。

import java.util.Scanner;

public class Calendar {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入年份:");
        int year = scanner.nextInt();
        System.out.print("请输入月份:");
        int month = scanner.nextInt();

        int[][] months = {
                {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
                {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
        };

        int days = months[isLeapYear(year)][month - 1];

        String[] weeks = {"日", "一", "二", "三", "四", "五", "六"};

        int weekIndex = getWeekIndex(year, month, 1);
        int lastMonthDays = getLastMonthDays(year, month);

        printCalendar(year, month, days, weeks, weekIndex, lastMonthDays);

        while (true) {
            System.out.print("请输入要查询的年份(上一年:preYear 下一年:nextYear):");
            String input = scanner.next();
            if ("preYear".equals(input)) {
                if (month == 1) {
                    year--;
                    month = 12;
                } else {
                    month--;
                }
            } else if ("nextYear".equals(input)) {
                if (month == 12) {
                    year++;
                    month = 1;
                } else {
                    month++;
                }
            } else {
                year = Integer.parseInt(input);
            }
            printCalendar(year, month, days, weeks, weekIndex, lastMonthDays);
        }
    }

    //打印日历
    public static void printCalendar(int year, int month, int days, String[] weeks, int weekIndex, int lastMonthDays) {
        System.out.println(year + "年" + month + "月");
        System.out.println("日\t一\t二\t三\t四\t五\t六");

        //打印上月的空格
        for (int i = 1; i < weekIndex; i++) {
            System.out.print("\t");
        }

        //打印上月的日期
        for (int i = lastMonthDays - weekIndex + 1; i <= lastMonthDays; i++) {
            System.out.print(i + "\t");
        }

        //打印当前月的日期
        for (int i = 1; i <= days; i++) {
            System.out.print(i + "\t");
            weekIndex++;
            if (weekIndex % 7 == 0) {
                System.out.println();
            }
        }

        //打印下月空格
        for (int i = 1; i <= 42 - weekIndex - lastMonthDays; i++) {
            System.out.print("\t");
        }
        System.out.println();
    }
}