JAVA將字符串CSV文件轉換為double []數組

Question

我的CSV文件有問題：這是該文件的示例。

4.98    24
9.14    21.6
4.03    34.7
2.94    33.4
5.33    36.2
5.21    28.7
12.43   22.9
19.15   27.1
29.93   16.5
17.1    18.9
20.45   15
13.27   18.9
15.71   21.7
8.26    20.4
10.26   18.2
8.47    19.9
6.58    23.1
14.67   17.5
11.69   20.2
11.28   18.2

目的是將其轉換為如下形式：

double[] column1= {4.98, 9.14, 4.03, 2.94, 5.33, 5.21, 12.43, 19.15}; //but with all the values, here it's just a sample
double [] column2 = {24, 21.6, 34.7, 33.4, 36.2, 28.7, 22.9, 27.1};

我不想寫所有數據，我需要做一個循環，但我不知道該怎么做。

我設法讀取csv文件並拆分數據，但沒有將結果轉換為double []數組。 這是我讀取文件的方式：

String fileName = "dataset.csv";
File file = new File(fileName);
String[] values;
try{
    Scanner inputStream = new Scanner(file);
    while (inputStream.hasNext()){
        String data = inputStream.next();
        values = data.split(",");
    }
    inputStream.close();

}
catch (FileNotFoundException e){
    e.printStackTrace();
}

Answer 1

您可以像執行流操作一樣，從文件中傳輸行並將其拆分以獲取String[] 。 然后，您可以流式傳輸每個這樣的數組並將每個項目轉換為double ，然后將它們收集回數組：

double[][] data =
    Files.lines(Paths.get(fileName))
         .map(s -> s.split(","))
         .map(s -> Arrays.stream(s).mapToDouble(Double::parseDouble).toArray())
         .toArray(double[][]::new);

Answer 2

這是Java 7的完整工作示例：

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;

public class Example
{
    public static void main(String args[])
    {
        Scanner inputStream = null;
        try
        {
            String fileName = "dataset.csv";
            File file = new File(fileName);

            // we don't know the amount of data ahead of time so we use lists
            List<Double> col1 = new ArrayList<>();
            List<Double> col2 = new ArrayList<>();

            inputStream = new Scanner(file);
            while (inputStream.hasNext())
            {
                String data = inputStream.next();
                String [] arr = data.split(",");

                col1.add(Double.parseDouble(arr[0]));
                col2.add(Double.parseDouble(arr[1]));
            }

            // Covert the lists to double arrays
            double[] column1 = new double[col1.size()];
            double[] column2 = new double[col2.size()];

            for (int i = 0; i < col1.size(); i++)
            {
                column1[i] = col1.get(i);
            }

            for (int i = 0; i < col2.size(); i++)
            {
                column2[i] = col2.get(i);
            }

            // print out just for verification
            System.out.println(Arrays.toString(column1));
            System.out.println(Arrays.toString(column2));
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }
        finally
        {
            if (inputStream != null)
            {
                inputStream.close();
            }
        }
    }
}