Question

我对下面的代码有疑问。我正在阅读一个包含大量数据的文件，其中一些内容是无关紧要的。数据写在一行，所以我不能使用nextLine或其他东西。

对于每个vertex，我将相关信息保存到dataperpoint。当我转到下一个顶点时，我想清除列表以填充新的相关信息。

我遇到的问题是，每次清除dataperpoint时，地图中的所有值都会被清除。当我尝试填充它时，Map中之前的所有位置都会得到相同的值。

我该如何做，并确保每个vertex都能获得自己的列表？

期待您的建议！

    public static Map<Integer, List<Double>> readData(File f) // throws IO exception? 
{
    // Create Map to store the vertex and list with relevant information in
    List<Double> dataperpoint = new ArrayList<Double>();
    Map<Integer, List<Double>> data = new HashMap<>();
    // Open the scanner
    try (Scanner in = new Scanner(f))
    {
        // To make sure the correct localization is used
        in.useLocale(Locale.US);

        // The first six integers contain irrelevant information
        for (int step = 1; step <= 6; step++)
        {
            in.nextInt();
        }

        // Do the information for vertex 0 separately, since it has one data point less
        int vertex = in.nextInt();
        for (int doubleinfo = 1; doubleinfo <= 4; doubleinfo++) // six relevant variables 
        {
            dataperpoint.add(in.nextDouble());
        }

        // irrelevant information
        for (int irrelevantinfo = 1; irrelevantinfo <= 2; irrelevantinfo++)
        {
            in.nextInt();
        }

        // Opening and Closing of time window
        dataperpoint.add((double) in.nextInt());
        dataperpoint.add((double) in.nextInt());

        data.put(vertex, dataperpoint);

        while (in.hasNext()) // think of different statement later
        {
            dataperpoint = new ArrayList<Double>();
            vertex = in.nextInt();

            for (int doubleinfo = 1; doubleinfo <= 4; doubleinfo++) // six relevant variables 
            {
                dataperpoint.add(in.nextDouble());
            }

            // irrelevant information
            for (int irrelevantinfo = 1; irrelevantinfo <= 3; irrelevantinfo++)
            {
                in.nextInt();
            }

            // Opening and Closing of time window
            dataperpoint.add((double) in.nextInt());
            dataperpoint.add((double) in.nextInt());

            data.put(vertex, dataperpoint);
        }
        in.close();
    }
    catch (FileNotFoundException e)
    {
        e.printStackTrace();
    }

Answer 1

使用LinkedHashMap＆lt;＆gt;而不是HashMap＆lt;＆gt;它应该解决你的问题。阅读此Difference between HashMap, LinkedHashMap and TreeMap

将多个列表放入地图中

1 个答案: