java - 使用数组作为 hashmap java 的键

Question

我有一个方法可以将一些值(从 excel 文件中获得)放入一个以数组为键的 HashMap 中

public HashMap<List<String>, List<String[]>> sbsBusServiceDataGnr() throws 
    IOException
{
    System.out.println(engine.txtY + "Processing HashMap "
        + "sbsBusServiceData..." + engine.txtN);
    int counterPass = 0, counterFail = 0, stopCounter = 0;
    String dataExtract, x = "";
    String[] stopInfo = new String[3];
    List<String[]> stopsData = new ArrayList<String[]>();
    List<String> serviceNum = new Vector<String>();

    HashMap<List<String>, List<String[]>> sbsBusServiceData = 
        new HashMap<List<String>, List<String[]>>();
    String dataPath = this.dynamicPathFinder(
        "Data\\SBS_Bus_Routes.csv");
    BufferedReader sbsBusServiceDataPop = new BufferedReader(
        new FileReader(dataPath));

    sbsBusServiceDataPop.readLine();
    //Skips first line
    while ((dataExtract = sbsBusServiceDataPop.readLine()) != null) {
        try {
            String[] dataParts = dataExtract.split(",", 5);
            if (!dataParts[4].equals("-")){
                if (Double.parseDouble(dataParts[4]) == 0.0){
                    sbsBusServiceData.put(serviceNum, stopsData);
                    String serviceNum1 = "null", serviceNum2 = "null";
                    if(!serviceNum.isEmpty()){
                        serviceNum1 = serviceNum.get(0);
                        serviceNum2 = serviceNum.get(1);
                    }
                    System.out.println("Service Number " + serviceNum1 
                        + ":" + serviceNum2 + " with " + stopCounter 
                        + " stops added.");
                    stopCounter = 0;
                    //Finalizing previous service

                    serviceNum.Clear();
                    serviceNum.add(0, dataParts[0]);
                    serviceNum.add(1, dataParts[1]);
                    //Adding new service
                }
            }
            stopInfo[0] = dataParts[2];
            stopInfo[1] = dataParts[3];
            stopInfo[2] = dataParts[4];
            stopsData.add(stopInfo);
            //Adding stop to service

            stopCounter++;
            counterPass++;
            }
        catch (Exception e) {
            System.out.println(engine.txtR + "Unable to process "
                + dataExtract + " into HashMap sbsBusServiceData." 
                + engine.txtN + e);
            counterFail++;
        }
    }
    sbsBusServiceDataPop.close();

    System.out.println(engine.txtG + counterPass + " number of lines"
        + " processed into HashMap sbsBusServiceData.\n" + engine.txtR
        + counterFail + " number of lines failed to process into "
        + "HashMap sbsBusServiceData.");

    return sbsBusServiceData;
}
//Generates sbsBusServiceDataGnr HashMap : 15376 Data Rows
//HashMap Contents: {ServiceNumber, Direction}, 
//    <{RouteSequence, bsCode, Distance}>

此方法用于将值放入 HashMap 中，但当我尝试调用它时，我似乎无法从 HashMap 中获取任何值，总是出现空指针异常

List<String> sbsTest = new Vector<String>();
    sbsTest.add(0, "10");
    sbsTest.add(1, "1");
    System.out.println(sbsBusServiceData.get(sbsTest));
    try{
        List<String[]> sbsServiceResults = sbsBusServiceData.get(sbsTest);
        System.out.println(sbsServiceResults.size());
        String x = sbsServiceResults.get(1)[0];
        System.out.println(x);
    } catch(Exception e){
        System.out.println(txtR + "No data returned" + txtN + e);
    }

这是我从以下位置读取数据的文件示例:

SBS

我怎样才能让 hashmap 返回我想要的值？

Answer 1

数组不适合作为 HashMap 中的键s，因为数组不会覆盖 Object的 equals和 hashCode方法(这意味着包含完全相同元素的两个不同数组实例将被 HashMap 视为不同的键)。

替代方案是使用 List<String>而不是 String[]作为 HashMap 的关键, 或者使用 TreeMap<String[]>自定义 Comparator<String[]>传递给构造函数。