java - 如何访问Java数组中的第一列数据并分配给另一个变量？

Question

我有一个 .txt 文件，其中包含一些值(已附上)。我需要对每一列数据执行平均和求和运算。读取文件后我无法访问列数据。 Data file

public class EEG {

    public static void main(String[] args)  {
        String pathToCsv = "C:\\Users\\Raghu\\Desktop\\EEG files\\testEEGData.txt"; 
        List<String> l2 = new ArrayList<>();
         l = readFileInList(pathToCsv);     

        for(int i = 0; i < 1; i++) 
              System.out.println(l.get(i));
            // I want to performe operation here, like sum and average of first column


    public static List<String> readFileInList(String fileName) 
      {       
        List<String> lines = Collections.emptyList(); 
        try
        { 
          lines = Files.readAllLines(Paths.get(fileName), StandardCharsets.UTF_8); 
        } 

        catch (IOException e) 
        { 
          e.printStackTrace(); 
        } 
        return lines; 
      } 

Answer 1

用逗号分割字符串并将第一个元素视为数字:

double value = Double.parseDouble(l.get(i).split(",")[0]);

映射列表:

List<Double> numbers = l.stream()
      .map(line -> Double.parseDouble(line.split(",")[0]))
      .collect(Collectors.toList());

并且可以计算总和:

numbers.stream().reduce(Double::sum)

放在一起:

List<String> l = readFileInList(pathToCsv); 

List<Double> numbers = l.stream()
      .map(line -> Double.parseDouble(line.split(",")[0]))
      .collect(Collectors.toList());

Double sum = numbers.stream().reduce(Double::sum).get();

Double avg = sum / numbers.size();