笔试题——用java实现股票交易日的判断

今天记录一道笔试题

1.原题：

需求：
股票交易或者分析会涉及到交易日的查询，为了分析高效快速，通常会把交易日放到内存中。要求实现下面的接口。

interface TradingDayService {//判断是否为交易日boolean isTradingDay(LocalDate date);//查询下一个交易日Optional<LocalDate> queryNextTradingDay(LocalDate date);//查询一段时间范围的交易日, 注意包括[from, to]List<LocalDate> queryBetween(LocalDate from, LocalDate to);//查询日期所属月份的第一个交易日Optional<LocalDate> queryFirstTradingDayOfMonth(LocalDate date)}

要求如下：
1 请用Java，Scala，Kotlin任意一种语言实现。
2. 访问速度足够快。
3. 尽量少占内存。
4. 有单元测试。

2.样本：（这里我只是列举了部分数据，完整的数据是一整年的数据。）

“2020-01-02”, “2020-01-03”, “2020-01-06”, “2020-01-07”, “2020-01-08”, “2020-01-09”, “2020-01-10”, “2020-01-13”, “2020-01-14”, “2020-01-15”, “2020-01-16”, “2020-01-17”, “2020-01-20”, “2020-01-21”, “2020-01-22”, “2020-01-23”, “2020-02-03”, “2020-02-04”, “2020-02-05”, “2020-02-06”, “2020-02-07”, “2020-02-10”, “2020-02-11”, “2020-02-12”, “2020-02-13”, “2020-02-14”, “2020-02-17”, “2020-02-18”, “2020-02-19”, “2020-02-20”, “2020-02-21”, “2020-02-24”, “2020-02-25”, “2020-02-26”, “2020-02-27”, “2020-02-28”, “2020-03-02”, “2020-03-03”, “2020-03-04”, “2020-03-05”, “2020-03-06”, “2020-03-09”, “2020-03-10”, “2020-03-11”, “2020-03-12”, “2020-03-13”, “2020-03-16”, “2020-03-17”, “2020-03-18”, “2020-03-19”, “2020-03-20”, “2020-03-23”, “2020-03-24”, “2020-03-25”, “2020-03-26”, “2020-03-27”, “2020-03-30”, “2020-03-31”, “2020-04-01”, “2020-04-02”, “2020-04-03”, “2020-04-07”, “2020-04-08”, “2020-04-09”, “2020-04-10”, “2020-04-13”。

3.解决思路：

（1）找数据规律
我们首先观察每个月的数据，查看交易日样本数据是否有规律。可以发现，毫无规律可言。。。

（2）认真阅读需求，提炼要点
读题，看要求，要求主要有两点：速度快、占内存少。任务就是实现这个TradingDayService接口的四个方法。看接口的参数、发现主要是对LocalDate运用的考察。

（3）如何存储样本数据：
第一种：交易日数据主要是用于查询，变动情况很好，考虑到要占用内存少，其实我们可以把这些样本数据存入redis里（实际开发用的比较多）。

第二种：使用一个单例来存储数据，该样本数据就只会占用一块内存空间。（其实在实际开发中，单例专门用于存储数据的情况很少，除非要用到该数据的多个处理方法，才会使用单例封装该数据和处理方法）

第三种：直接使用一个静态的集合，来存储。
采用：因为题目中，没有说明可以使用redis，所有我个人采用了单例模式来存储该数据。数据的存储，大家根据实际的需求来看。

5.话不多说，直接上代码

单例类

package singleton;import java.time.LocalDate;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;public class TradingDayDataSingleton {private List<String> tradingDayData = Arrays.asList("2020-01-02", "2020-01-03", "2020-01-06", "2020-01-07", "2020-01-08", "2020-01-09", "2020-01-10", "2020-01-13", "2020-01-14", "2020-01-15", "2020-01-16", "2020-01-17", "2020-01-20", "2020-01-21", "2020-01-22", "2020-01-23","2020-02-03", "2020-02-04", "2020-02-05", "2020-02-06", "2020-02-07", "2020-02-10", "2020-02-11", "2020-02-12", "2020-02-13", "2020-02-14", "2020-02-17", "2020-02-18", "2020-02-19", "2020-02-20", "2020-02-21", "2020-02-24", "2020-02-25","2020-02-26", "2020-02-27", "2020-02-28", "2020-03-02", "2020-03-03", "2020-03-04", "2020-03-05", "2020-03-06", "2020-03-09", "2020-03-10", "2020-03-11", "2020-03-12", "2020-03-13", "2020-03-16", "2020-03-17", "2020-03-18", "2020-03-19","2020-03-20", "2020-03-23", "2020-03-24", "2020-03-25", "2020-03-26", "2020-03-27", "2020-03-30", "2020-03-31", "2020-04-01", "2020-04-02", "2020-04-03", "2020-04-07", "2020-04-08", "2020-04-09", "2020-04-10", "2020-04-13", "2020-04-14","2020-04-15", "2020-04-16", "2020-04-17", "2020-04-20", "2020-04-21", "2020-04-22", "2020-04-23", "2020-04-24", "2020-04-27", "2020-04-28", "2020-04-29", "2020-04-30", "2020-05-06", "2020-05-07", "2020-05-08", "2020-05-11", "2020-05-12","2020-05-13", "2020-05-14", "2020-05-15", "2020-05-18", "2020-05-19", "2020-05-20", "2020-05-21", "2020-05-22", "2020-05-25", "2020-05-26", "2020-05-27", "2020-05-28", "2020-05-29", "2020-06-01", "2020-06-02", "2020-06-03", "2020-06-04","2020-06-05", "2020-06-08", "2020-06-09", "2020-06-10", "2020-06-11", "2020-06-12", "2020-06-15", "2020-06-16", "2020-06-17", "2020-06-18", "2020-06-19", "2020-06-22", "2020-06-23", "2020-06-24", "2020-06-29", "2020-06-30", "2020-07-01","2020-07-02", "2020-07-03", "2020-07-06", "2020-07-07", "2020-07-08", "2020-07-09", "2020-07-10", "2020-07-13", "2020-07-14", "2020-07-15", "2020-07-16", "2020-07-17", "2020-07-20", "2020-07-21", "2020-07-22", "2020-07-23", "2020-07-24","2020-07-27", "2020-07-28", "2020-07-29", "2020-07-30", "2020-07-31", "2020-08-03", "2020-08-04", "2020-08-05", "2020-08-06", "2020-08-07", "2020-08-10", "2020-08-11", "2020-08-12", "2020-08-13", "2020-08-14", "2020-08-17", "2020-08-18","2020-08-19", "2020-08-20", "2020-08-21", "2020-08-24", "2020-08-25", "2020-08-26", "2020-08-27", "2020-08-28", "2020-08-31", "2020-09-01", "2020-09-02", "2020-09-03", "2020-09-04", "2020-09-07", "2020-09-08", "2020-09-09", "2020-09-10","2020-09-11", "2020-09-14", "2020-09-15", "2020-09-16", "2020-09-17", "2020-09-18", "2020-09-21", "2020-09-22", "2020-09-23", "2020-09-24", "2020-09-25", "2020-09-28", "2020-09-29", "2020-09-30", "2020-10-09", "2020-10-12", "2020-10-13","2020-10-14", "2020-10-15", "2020-10-16", "2020-10-19", "2020-10-20", "2020-10-21", "2020-10-22", "2020-10-23", "2020-10-26", "2020-10-27", "2020-10-28", "2020-10-29", "2020-10-30", "2020-11-02", "2020-11-03", "2020-11-04", "2020-11-05","2020-11-06", "2020-11-09", "2020-11-10", "2020-11-11", "2020-11-12", "2020-11-13", "2020-11-16", "2020-11-17", "2020-11-18", "2020-11-19", "2020-11-20", "2020-11-23", "2020-11-24", "2020-11-25", "2020-11-26", "2020-11-27", "2020-11-30","2020-12-01", "2020-12-02", "2020-12-03", "2020-12-04", "2020-12-07", "2020-12-08", "2020-12-09", "2020-12-10", "2020-12-11", "2020-12-14", "2020-12-15", "2020-12-16", "2020-12-17", "2020-12-18", "2020-12-21", "2020-12-22", "2020-12-23","2020-12-24", "2020-12-25", "2020-12-28", "2020-12-29", "2020-12-30", "2020-12-31");private TradingDayDataSingleton() {}private static class TradingDayData {private static final TradingDayDataSingleton instance = new TradingDayDataSingleton();}public static TradingDayDataSingleton getInstance(){return TradingDayData.instance;}public List<String> getTradingDayData() {return tradingDayData;}public void setTradingDayData(List<String> tradingDayData) {this.tradingDayData = tradingDayData;}/*** 把所有的交易日字符串类型转换为LocalDate类型* @return*/public List<LocalDate> tradingDaysString2LocalDate() {List<LocalDate> localDates = new ArrayList<>();List<String> tradingDayData = getTradingDayData();tradingDayData.forEach(t->{LocalDate localDate = LocalDate.parse(t);localDates.add(localDate);});return localDates;}
}

接口类

public interface TradingDayService {//判断是否为交易日boolean isTradingDay(LocalDate date);//查询下一个交易日Optional<LocalDate> queryNextTradingDay(LocalDate date);//查询一段时间范围的交易日, 注意包括[from, to]List<LocalDate> queryBetween(LocalDate from, LocalDate to);//查询日期所属月份的第一个交易日Optional<LocalDate> queryFirstTradingDayOfMonth(LocalDate date);
}

接口实现类

public class TradingDayServiceImpl implements TradingDayService {@Overridepublic boolean isTradingDay(LocalDate date) {DateTimeFormatter format = DateTimeFormatter.ofPattern("yyyy-MM-dd");String day = format.format(date);List<String> allTradingDay = TradingDayDataSingleton.getInstance().getTradingDayData();return allTradingDay.contains(day);}@Overridepublic Optional<LocalDate> queryNextTradingDay(LocalDate date) {//下一天日期LocalDate nextDay = date.plusDays(1L);//哨兵，防止死循环int flag = 0;while (true) {//判断下一天是否是交易日boolean tradingDay = this.isTradingDay(nextDay);if (tradingDay == true) {break;}flag++;nextDay = nextDay.plusDays(1L);if (flag == 365) {nextDay = null;break;}}return Optional.ofNullable(nextDay);}@Overridepublic List<LocalDate> queryBetween(LocalDate from, LocalDate to) {int duringDays = to.getDayOfYear() - from.getDayOfYear();LinkedList<LocalDate> localDates = new LinkedList<>();for (int i = 0; i <= duringDays; i++) {LocalDate date = from.plusDays(Long.parseLong(String.valueOf(i)));if (this.isTradingDay(date)) {localDates.add(date);}}return localDates;}@Overridepublic Optional<LocalDate> queryFirstTradingDayOfMonth(LocalDate date) {int dayOfMonth = date.getDayOfMonth();LocalDate day = date.minusDays(dayOfMonth);return this.queryNextTradingDay(day);}}

测试用例类

public class TradingDayServiceTest {private static TradingDayService tradingDayService = new TradingDayServiceImpl();public static void main(String[] args) {long start = System.currentTimeMillis();//testTradingDay();  耗时0.4s--0.5s//testQueryNextTradingDay(); 耗时 0.36s左右//testQueryFirstTradingDayOfMonth(); 耗时：0.2s--0.5stestQueryBetween(); //0.2s--0.3sSystem.out.println(System.currentTimeMillis() - start);}public static void testTradingDay(){LocalDate date = LocalDate.parse("2020-02-04");System.out.println(tradingDayService.isTradingDay(date));}public static void testQueryNextTradingDay() {DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");LocalDate localDate = LocalDate.parse("2020-12-04");Optional<LocalDate> tradingDate = tradingDayService.queryNextTradingDay(localDate);tradingDate.ifPresent(u->{System.out.println(u.format(formatter));;});}public static void testQueryFirstTradingDayOfMonth(){LocalDate date = LocalDate.parse("2020-12-24");Optional<LocalDate> localDate = tradingDayService.queryFirstTradingDayOfMonth(date);localDate.ifPresent(u->{System.out.println(u.format(DateTimeFormatter.ofPattern("yyyy-MM-dd")));});}public static void testQueryBetween(){LocalDate from = LocalDate.parse("2021-01-02");LocalDate to = LocalDate.parse("2022-02-13");List<LocalDate> localDates = tradingDayService.queryBetween(from, to);localDates.forEach(u->{System.out.println(u.toString());});}
}

以上就是我的实现方式。写的不好，大家可以提出建议，加依修改。我只是以个人的想法实现的代码，肯定有很多不足之处，欢迎大家评论。