JAVA实现，输入年月日，输出这是一年的第几天，是星期几

目录

1、不引入额外的包

2、通过日期相关API实现

---

两种实现

• 不引入额外的包
• 通过日期相关API实现

1、不引入额外的包

import java.util.Scanner;

/**
 * Hello world!
 */
public class App {
    
    public static void main(String[] args) {
        // 控制台输入 年 月 日，空格隔开
        Scanner in = new Scanner(System.in);
        String str = in.nextLine();
        String[] ymd = str.split(" ");

        Integer year = Integer.valueOf(ymd[0]);
        Integer month = Integer.valueOf(ymd[1]);
        Integer day = Integer.valueOf(ymd[2]);
        int days = getDay(year, month, day);
        int weekDay = getWeekDay(year, month, day);
        System.out.println(days + " " + weekDay);
    }

    /**
     * 获取当前日期是当前年的第几天
     *
     * @param year  年
     * @param month 月
     * @param day   日
     * @return
     */
    static int getDay(int year, int month, int day) {
        int tmp = 0;
        switch (month) {
            case 12:
                tmp = tmp + 30;
            case 11:
                tmp = tmp + 31;
            case 10:
                tmp = tmp + 30;
            case 9:
                tmp = tmp + 31;
            case 8:
                tmp = tmp + 31;
            case 7:
                tmp = tmp + 30;
            case 6:
                tmp = tmp + 31;
            case 5:
                tmp = tmp + 30;
            case 4:
                tmp = tmp + 31;
            case 3:
                tmp = tmp + 28;
            case 2:
                tmp = tmp + 31;
            case 1:
                tmp = tmp + day;
        }
        // 判断是否闰年，且是3月以后，此时天数+1
        if ((year % 400 == 0 || year % 4 == 0 && year % 100 != 0) && month >= 3) {
            tmp = tmp + 1;
        }
        return tmp;
    }

    /**
     * 获取当前年共多少天
     *
     * @param year 年
     * @return
     */
    static int yearAllDays(int year) {
        int tmp = 365;
        // 判断是否闰年
        if (year % 400 == 0 || year % 4 == 0 && year % 100 != 0) {
            tmp = 366;
        }
        return tmp;
    }

    /**
     * 获取当前日期是星期几
     *
     * @param year  年
     * @param month 月
     * @param day   日
     * @return
     */
    static int getWeekDay(int year, int month, int day) {
        int tmp = 0;
        for (int i = 1923; i < year; i++) {
            tmp = tmp + yearAllDays(i);
        }
        tmp = tmp + getDay(year, month, day);
        return tmp % 7;
    }
}

2、通过日期相关API实现

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

public class Main {
    
    public static void main(String[] args) {
        // 控制台输入 年 月 日，空格隔开
        Scanner in = new Scanner(System.in);
        String str = in.nextLine();
        String[] ymd = str.split(" ");

        getWeekDayAndYearDayByJdk(ymd);
    }

    static void getWeekDayAndYearDayByJdk(String[] arr) {
        String dateStr = arr[0] + "-" + arr[1] + "-" + arr[2];
        SimpleDateFormat f = new SimpleDateFormat("yyyy-MM-dd");
        Date date = null;
        try {
            date = f.parse(dateStr);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        Calendar instance = Calendar.getInstance();
        instance.setTime(date);
        int yearDay = instance.get(Calendar.DAY_OF_YEAR);
        int weekDay = instance.get(Calendar.DAY_OF_WEEK);
        System.out.println(yearDay + " " + (weekDay - 1)%6);
    }
}