如何将csv文件中的数字保存到java arraylist中

Question

您好，这是我第一次发布，请让我知道如果我在问题询问过程中做错了什么。

我的目的是：在csv文件中保存双重变量并将它们保存在java文件中的ArrayList中。

我到目前为止有当前的代码，我在java的初学者，所以请不要火焰在ToT

import java.io.*; 
import java.util.*; 
import java.lang.*; 

public class CsvProcessor { 

    public static void main(String[] args) { 
     Scanner keyboard = new Scanner(System.in); 

     // ask for file path at command prompt, save the path input in path 
     System.out.print("path of file: "); 
     String path = keyboard.next(); 

     try { 
      // set up file, reader, and arraylist for processing csv file 
      java.io.File csv = new java.io.File(path); 
      BufferedReader bufferedReader = new BufferedReader(new FileReader(csv)); 
      ArrayList<String> csvEntry = new ArrayList<String>(); 

      // set parameters for StringTokenizer 
      String line = ""; 
      String delimiter = ","; 

      //read using bufferedReader and save using csvEntry ArrayList 
      while ((line = bufferedReader.readLine()) != null) {  
       StringTokenizer stringTokenizer = new StringTokenizer(line, delimiter); 
       while (stringTokenizer.hasMoreTokens()) { 
        csvEntry.add(stringTokenizer.nextToken()); 
       } 
      } 

      csvEntry.toArray(); 
      double[] csvDouble = new double[csvEntry.getLength()]; 
      for (int i = 0; i < csvEntry.getLength(); i++) { 
       csvDouble[i] = Double.parseDouble(csvEntry[i]); 
      } 

      int x = csvDouble.getLength(); 
      double sum = 0; 

      for (int y = 0; y < x; y++) { 
       sum = sum + csvDouble[y]; 
      } 

      double mean = sum/x; 
      System.out.println("mean is: " + mean); 
      bufferedReader.close(); 
     } catch (FileNotFoundException e) { 
      e.printStackTrace(); 
     } catch (IOException e) { 
      e.printStackTrace(); 
     } 

    } 
} 

我试图像在CSV文件转换的字符串，并将它们保存到ArrayList中，然后将事情将ArrayList转换为数组，然后将其转换为double数组。 我得到的错误是：

C:\Users\user\Codes\ktrt>java CsvProcessor 
path of file: C:\Users\user\Codes\ktrt\montyreal.csv 
Exception in thread "main" java.lang.NumberFormatException: For input string: "5 
48.53" 
     at java.lang.NumberFormatException.forInputString(Unknown Source) 
     at java.lang.Integer.parseInt(Unknown Source) 
     at java.lang.Integer.<init>(Unknown Source) 
     at CsvProcessor.main(csvprocessor.java:27) 

非常感谢你的帮助。

Answer 1

首先，你有一个错误的错误日志。您的代码没有Integer.parseInt()方法。比方说，你正确地解析CSV到csvEntry变量，这是你可以做什么：

List<Double> csvDouble = new ArrayList<Double>(); 
double mean, total = 0; 

for (String raw : csvEntry) { 
    double entry = Double.valueOf(raw); 
    total += entry; 
    csvDouble.add(entry); 
} 

mean = total/csvDouble.size(); 
// at this point you have your ArrayList and mean value; 
System.out.println("mean is " + mean); 

希望这有助于:)