java-输出指定要求的回文日期

编写程序

package c02.s01.p07;

import java.util.Scanner;


public class PalindromicDate {
    public static void main(String[] args) {
        String strDate;
        int year, month, day;
        Scanner sc = new Scanner(System.in);

        System.out.print("输入8位数构成的日期：");
        strDate = sc.next();

        if (isLegalDate(strDate)) {
            System.out.println("[" + strDate + "]是合法日期~");
        } else {
            System.out.println("[" + strDate + "]是非法日期~");
        }
    }
    
    private static boolean isLegalDate(String strDate) {
        int year, month, day;
        year = Integer.parseInt(strDate.substring(0, 4));
        month = Integer.parseInt(strDate.substring(4, 6));
        day = Integer.parseInt(strDate.substring(6));

        // 利用反向思维来处理
        if (year < 1000 || year > 8999) return false;
        if (month < 1 || month > 12) return false;
        if (month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10 || month == 12) {
            if (day < 1 || day > 31) return false;
        } else if (month == 2) {
            if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) { // 闰年判断
                if (day < 1 || day > 29) return false;
            } else {
                if (day < 1 || day > 28) return false;
            }
        } else {
            if (day < 1 || day > 30) return false;
        }
        return true;
    }
}

运行程序，查看结果

月份和天日不对

长度不对

完整代码

package c02.s01.p07;

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Scanner;


public class PalindromicDate {
    public static void main(String[] args) {
        String strDate = "";
        int year, month, day;
        Calendar calendar = Calendar.getInstance();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");
        Scanner sc = new Scanner(System.in);

        System.out.print("输入8位数构成的日期：");
        strDate = sc.next();

        if (isLegalDate(strDate)) {
            System.out.println("[" + strDate + "]是合法日期~");
            // 用户输入的日期作为起点
            year = Integer.parseInt(strDate.substring(0, 4));
            month = Integer.parseInt(strDate.substring(4, 6));
            day = Integer.parseInt(strDate.substring(6));
            calendar.set(Calendar.YEAR, year);
            calendar.set(Calendar.MONTH, month - 1);
            calendar.set(Calendar.DAY_OF_MONTH, day);
            // 任务1、输出该日期之后的第一个回文日期
            String strDate1 = "";
            Calendar calendar1 = calendar;
            while (true) {
                calendar1.add(Calendar.DAY_OF_MONTH, 1); // 往后推1天
                strDate1 = sdf.format(calendar1.getTime());
                if (isPalindromDate(strDate1)) {
                    break; // 找到一个回文日期就跳出循环
                }
            }
            System.out.println("该日期之后的第一个回文日期：" + strDate1);
            // 任务2、输出该日期之后的第一个ABABBABA型回文日期
            String strDate2 = "";
            Calendar calendar2 = calendar;
            while (true) {
                calendar2.add(Calendar.DAY_OF_MONTH, 1); // 往后推1天
                strDate2 = sdf.format(calendar2.getTime());
                if (isABABBABADate(strDate2)) {
                    break; // 找到一个回文日期就跳出循环
                }
            }
            System.out.println("该日期之后的第一个ABABBABA型日期：" + strDate2);
        } else {
            System.out.println("[" + strDate + "]是非法日期~");
        }
    }

    
    private static boolean isLegalDate(String strDate) {
        int year, month, day;
        year = Integer.parseInt(strDate.substring(0, 4));
        month = Integer.parseInt(strDate.substring(4, 6));
        day = Integer.parseInt(strDate.substring(6));

        // 利用反向思维来处理
        if (year < 1000 || year > 8999) return false;
        if (month < 1 || month > 12) return false;
        if (month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10 || month == 12) {
            if (day < 1 || day > 31) return false;
        } else if (month == 2) {
            if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) { // 闰年判断
                if (day < 1 || day > 29) return false;
            } else {
                if (day < 1 || day > 28) return false;
            }
        } else {
            if (day < 1 || day > 30) return false;
        }
        return true;
    }

    
    private static boolean isPalindromDate(String strDate) {
        for (int i = 0; i < 4; i++) {
            // 采用反向思维
            if (strDate.charAt(i) != strDate.charAt(7 - i)) return false;
        }
        return true;

        }
    
    private static boolean isABABBABADate(String strDate) {
        if (isPalindromDate(strDate)) {
            if (strDate.charAt(0) == strDate.charAt(2) && strDate.charAt(1) == strDate.charAt(3)) {
                return true;
            }
        }
        return false;
    }
}

运行程序，查看结果