Question

我对CSV文件有疑问：这是该文件的示例。

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

目的是将其转换成类似的东西：

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};

我不想写所有数据，我需要做一个循环，但我不知道我该怎么做。

我设法读取csv文件并拆分数据，但不将结果转换为double []数组。以下是我阅读文件的方法：

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

您可以流式传输文件中的行并将其拆分为String[]，就像您一样。然后，您可以流式传输每个此类数组并将每个项目转换为double，然后将它们收集回数组：

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

这是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();
            }
        }
    }
}

JAVA将字符串CSV文件转换为double []数组

2 个答案: