业务上需要开发一个获取连续签到(打卡)天数的功能，修修改改多次后发现了规律，可以减少代码量，使程序更简洁明了。

核心是getContinuousSignInDay方法的逻辑，每次用当前时间去比较，规律是比较的天数是递增的(连续签到的情况下)。

这份代码脱去了业务上的逻辑，只有签到的功能demo

import lombok.Data;

import java.text.ParseException;

import java.text.SimpleDateFormat;

import java.util.ArrayList;

import java.util.Date;

import java.util.List;

/**

* @Description TODO

* @Author fangyunhe

* @Date 2019/8/15 17:41

* Version 1.0

**/

public class SignInTest {

@Data

static

class SignIn{

private Date signInDay;

public SignIn(){

}

public SignIn(String day) throws ParseException {

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

signInDay = sdf.parse(day);

}

}

public static void main(String[] args) throws Exception{

ListsignInList = new ArrayList<>();

signInList.add(new SignIn("2019-08-15"));

signInList.add(new SignIn("2019-08-14"));

//signInList.add(new SignIn("2019-08-13"));

signInList.add(new SignIn("2019-08-12"));

signInList.add(new SignIn("2019-08-11"));

int continuousSignInDay = getContinuousSignInDay(signInList);

System.out.println("连续签到日期："+ continuousSignInDay);

}

/**

* 连续签到天数

*

* @return int

* @Author fangyunhe

* @Date 2019-08-15 17:16:01

* @Param

**/

private static int getContinuousSignInDay(ListsignInList) {

//continuousDay 连续签到数

int continuousDay = 1;

boolean todaySignIn = false;

Date today = new Date();

for (int i = 0; i < signInList.size(); i++) {

SignIn signIn = signInList.get(i);

int intervalDay = distanceDay(today, signIn.getSignInDay());

//当天签到

if (intervalDay == 0 && i == 0) {

todaySignIn = true;

}

else if (intervalDay == continuousDay) {

continuousDay++;

}else {

//不连续，终止判断

break;

}

}

if (!todaySignIn) {

continuousDay--;

}

return continuousDay;

}

/**

* 两个日期对比间隔天数

*

* @param smallDay

* @return boolean

* @Author fangyunhe

* @Date 2019-08-13 18:42:41

* @Param largeDay

**/

private static int distanceDay(Date largeDay, Date smallDay) {

int day = (int) ((largeDay.getTime() - smallDay.getTime()) / (1000 * 60 * 60 * 24));

return day;

}

}