Java中使用Stream筛选股票最低收盘价出错问题排查

我有一份股票交易所的CSV数据文件，读取后需按条件打印数据，要求展示每只股票的最低收盘价。但我的代码仅显示三只股票的第一条记录，无法正确获取最低值，请问我的Stream筛选逻辑哪里出错了？

我的代码 #

private static void smallestPriceByStock(List<String> stocks) throws ParseException {
    List<StockPrice> stockPrices = new ArrayList<>();
    HashSet<String> stock = new HashSet<>();
    SimpleDateFormat sdfOriginal = new SimpleDateFormat("yyyy-MM-dd");
    SimpleDateFormat sdfNovaData = new SimpleDateFormat("dd/MM/yyyy");

    try {
        for (String s : stocks) {
            String[] array = a.split(",");
            String name = array[0];
            String date = array[1];
            Date dataOriginal = sdfOriginal.parse(date);
            float fechamento = Float.parseFloat(array[2]);
            long volume = Long.parseLong(array[3]);
            StockPrice stockPrice = new StockPrice(nome, dataOriginal, price, volume);
            stockPrices.add(stockPrice);
            Stock st = new Stock(name);
            st.addStockPrice(stockPrice);
            stock.add(st.getNome());

        }
        System.out.println("Menores fechamentos");
        List<Cotacao> cotas = new ArrayList<>();
        double smallestValue = 0;
        for(String a : acao) {
            for (Cotacao c : cotacoes) {
                if (c.getNome().contains(a)) {
                    smallestValue = cotacoes.stream()
                            .filter(x -> x.getNome() == a)
                            .mapToDouble(x -> x.getValue()).summaryStatistics().getMax();
                        System.out.println("Stock: " + c.getNome() + ", " + "Price: " + smallestValue + ", " + "Date: " + sdfNovaData.format(c.getData()));
                        break;
                    }
                }
            }

        for(Cotacao cotacao : cotas){
            System.out.println(cotacao.getNome());
        }
        System.out.println();
    } catch (UnsupportedOperationException | ParseException e) {
        throw new UnsupportedOperationException("calculaMenorFechamentoPorAcao não implementado", e);
    }
}

CSV文件示例 #

Acao,Data,Fechamento,Volume
OGXP3,2013-01-01,4.38,0
OGXP3,2013-01-02,4.76,45904000
OGXP3,2013-01-03,4.90,38143400
PETR4,2013-01-02,19.69,30182600
PETR4,2013-01-03,20.40,30552600
PETR4,2013-01-04,20.43,36141000
PETR4,2013-01-07,20.08,28069600
VALE5,2013-01-01,40.87,0
VALE5,2013-01-02,42.60,18515700
VALE5,2013-01-03,42.09,15001800
VALE5,2013-01-04,41.36,26351900

问题分析与修正 #

核心错误点 #

1. 变量未正确初始化/引用错误

   • cotas列表全程为空，没有添加任何数据，遍历它的循环根本不会执行
   • 循环变量错误：a.split(",")中的a应该是当前循环的s；StockPrice构造器里的nome应为name，price应为fechamento
   • 未定义的变量：acao集合不存在，应该使用之前定义的stock集合

2. Stream逻辑完全错误

   • 字符串比较用x.getNome() == a：这是引用比较，不是内容比较，应该用x.getNome().equals(a)
   • 调用getMax()而非getMin()：直接取了最大值，完全违背“最低收盘价”的需求
   • 从空的cotas流中获取数据：自然得不到有效结果

3. 流程逻辑错误

   • 即使cotas有数据，找到第一个匹配的记录就break，只会输出第一条记录，而非最低值对应的记录

修正后的代码 #

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.*;
import java.util.stream.Collectors;

private static void smallestPriceByStock(List<String> stocks) throws ParseException {
    SimpleDateFormat sdfOriginal = new SimpleDateFormat("yyyy-MM-dd");
    SimpleDateFormat sdfNovaData = new SimpleDateFormat("dd/MM/yyyy");

    List<StockPrice> stockPrices = new ArrayList<>();
    for (String s : stocks) {
        // 跳过CSV表头行
        if (s.startsWith("Acao")) continue;
        String[] array = s.split(",");
        String stockName = array[0];
        Date date = sdfOriginal.parse(array[1]);
        float closingPrice = Float.parseFloat(array[2]);
        long volume = Long.parseLong(array[3]);
        stockPrices.add(new StockPrice(stockName, date, closingPrice, volume));
    }

    System.out.println("Menores fechamentos");
    // 按股票名称分组，筛选出每组收盘价最低的记录
    Map<String, Optional<StockPrice>> minPriceMap = stockPrices.stream()
            .collect(Collectors.groupingBy(StockPrice::getStockName,
                    Collectors.minBy(Comparator.comparingDouble(StockPrice::getClosingPrice))));

    // 遍历输出结果
    minPriceMap.forEach((name, minPriceOpt) -> {
        minPriceOpt.ifPresent(price -> {
            System.out.printf("Stock: %s, Price: %.2f, Date: %s%n",
                    name,
                    price.getClosingPrice(),
                    sdfNovaData.format(price.getDate()));
        });
    });
}

// 配套的StockPrice实体类
class StockPrice {
    private String stockName;
    private Date date;
    private float closingPrice;
    private long volume;

    public StockPrice(String stockName, Date date, float closingPrice, long volume) {
        this.stockName = stockName;
        this.date = date;
        this.closingPrice = closingPrice;
        this.volume = volume;
    }

    public String getStockName() {
        return stockName;
    }

    public Date getDate() {
        return date;
    }

    public float getClosingPrice() {
        return closingPrice;
    }
}

修正说明 #

• 先正确解析CSV数据，跳过表头，填充stockPrices列表
• 使用Collectors.groupingBy按股票名称分组，结合Collectors.minBy和比较器，直接获取每组收盘价最低的记录
• 用forEach遍历分组结果，输出对应股票名称、最低收盘价及对应日期
• 修复了字符串比较、变量引用等低级错误，确保逻辑符合需求

内容的提问来源于stack exchange，提问作者Marco Aurélio Lopes Júnior