在Java中读取CSV文件时出现NumberFormatException

Question

我是Java的初学者，有点卡在这两个问题中，所以我试图让程序逐行从CSV文件读取。

因此，在文件中，第一行为String，列为double。 所以问题是当它读取第一行时，它正在读取标题为双精度的字，这给了我一个错误。

顺便是CSV文件

我得到的错误是在线程“ main”下的以下异常java.lang.NumberFormatException：对于输入字符串：“ CLOSE”这是第一个错误

第二个错误>>在sun.misc.FloatingDecimal.readJavaFormatString（FloatingDecima：l.java：1222）–

第三个错误>>在java.lang.Double.parseDouble（Double.java:510）

在AlgorithmTrader.ReadInputData（AlgorithmTrader.java:63）上出现第四次错误>>>

第五错误>> at AlgorithmTrader.Run（AlgorithmTrader.java:16）

最后一个错误>> SimpleAlgorithmTradingPlatform.main（SimpleAlgorithmTradingPlatform.java:15）

因此，文件的第一行具有TIMESTAMP | 关闭| 高| 低| 打开 体积，在这些行的每一行下都有双倍的数字，但体积有整数

您的建议将不胜感激。 谢谢

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Scanner;

public class AlgorithmTrader {

    public void Run() {

        ReadInputData();
    }

    public void ReadInputData() {

        // create object of scanner class for user input
        Scanner scan = new Scanner(System.in);
        // declare file name for input file
        String inputFileName = "";

        // input from user for input file
        System.out.print("Enter Input File Name: ");
        inputFileName = scan.nextLine();
        try {
            PrintWriter pw = new PrintWriter("output.csv");// to open the file

            // create a new file
            File file = new File(inputFileName);
            // create a new scanner object to read file
            Scanner readFile = new Scanner(file);

            // for each line data
            String line = "";

            line = readFile.nextLine();//skip the first line

            while (readFile.hasNextLine()) {

                readFile.nextLine();
                // pass file to scanner again
                readFile = new Scanner(file);

                ArrayList<String> list = new ArrayList<String>();

                // read stock data line by line

                while (readFile.hasNextLine()) {
                    // read line from file
                    line = readFile.nextLine();
                    // split line data into tokens
                    String result[] = line.split(",");

                    // variables to create a Stock object

                    String timestamp = result[0];
                    double close = Double.parseDouble(result[1]);
                    double high = Double.parseDouble(result[2]);
                    double low = Double.parseDouble(result[3]);
                    double open = Double.parseDouble(result[4]);
                    int volume = Integer.parseInt(result[5]);

                    // store data into ArrayList
                    list.add(readFile.next());
                    pw.print(list.add(readFile.next()));

                    Stock stock = new Stock(timestamp, close, high, low, open, volume);
                }// end of while to read file

                //close readFile object
                readFile.close();
                pw.close();//close file
            }
        } catch (FileNotFoundException e1) {

            System.out.println(" not found.\n");
            System.exit(0);
        } catch (IOException e2) {
            System.out.println("File can't be read\n");
        }
    }
}

我还有另一个文件库存类

public class Stock {

    String timestamp;

    double close;
    double high;
    double low;
    double open;
    int volume;

    Stock(String t, double c, double h, double l, double o, int v) {
        timestamp = t;
        close = c;
        high = h;
        low = l;
        open = o;
        volume = v;
    }

    public void settimestamp(String t) {
        this.timestamp = t;
    }

    public void setclose(double c) {
        this.close = c;
    }

    public void sethigh(double h) {
        this.high = h;
    }

    public void setopen(double o) {
        this.open = o;
    }

    public void setvolume(int v) {
        this.volume = v;
    }

    public String gettimestamp() {
        return timestamp;
    }

    public double close() {
        return close;
    }

    public double high() {
        return high;
    }

    public int volume() {
        return volume;
    }
}

而且另一个文件中的main方法也是如此

import java.text.DecimalFormat;

public class SimpleAlgorithmTradingPlatform {

    public static void main(String[] args) {

        DecimalFormat fmt = new DecimalFormat("#0.00"); // to get the      DecimalFormat

        AlgorithmTrader test = new AlgorithmTrader();

        test.Run();
    }
}

Answer 1

您遇到NumberFormatException是因为这里

line = readFile.nextLine();//skip the first line 

您不会跳过第一行。 获取文件名后，最好使用BufferedReader而不是Scanner。 我已经更正了您的代码。

import java.io.*;
import java.util.ArrayList;
import java.util.Scanner;

public class AlgorithmTrader {

    public void Run() {
        ReadInputData();
    }

    public void ReadInputData() {

        // create object of scanner class for user input
        Scanner scan = new Scanner(System.in);
        // declare file name for input file
        String inputFileName = "";

        // input from user for input file
        System.out.print("Enter Input File Name: ");
        inputFileName = scan.nextLine();

        // create a new file
        File csvFile = new File(inputFileName);
        String line;
        ArrayList<Stock> list = new ArrayList<>();

        try (BufferedReader br = new BufferedReader(new FileReader(csvFile))) {

            System.out.println("Reading file " + csvFile);

            System.out.println("Skipping title of the CSV file");
            // Skip first line because it is title
            br.readLine();

            System.out.println("Converting line to Stock");

            while ((line = br.readLine()) != null) {

                String result[] = line.split(",");
                String timestamp = result[0];
                double close = Double.parseDouble(result[1]);
                double high = Double.parseDouble(result[2]);
                double low = Double.parseDouble(result[3]);
                double open = Double.parseDouble(result[4]);
                int volume = Integer.parseInt(result[5]);

                list.add(new Stock(timestamp, close, high, low, open, volume));
            }

            System.out.println("Done");

        } catch (FileNotFoundException e1) {
            System.out.println(" not found.");
            System.exit(0);
        } catch (IOException e2) {
            System.out.println("File can't be read");
        }
    }
}

Answer 2

很高兴看到CSV文件中内容的虚构示例，但请不要给我们其他任何注释。 ;）

看来您的错误（可能是所有错误）最有可能来自您的股票类别。 这是另一个发布的问题，但是您的获取者和安装者需要注意。 一些也丢失了，但是也许这是选择。

您应该能够使用一个Scanner对象和一个while循环来执行此任务。 使用相同的Scanner对象进行用户输入和文件读取，无论如何都会对其进行初始化。

下面的代码是一种实现方法：

ArrayList<String> list = new ArrayList<>();
// create object of scanner class for user input
// and File Reading.
Scanner scan = new Scanner(System.in);
// declare file name for input file
String inputFileName = "";
// input from User for input file name.
System.out.print("Enter Input File Name: ");
inputFileName = scan.nextLine();

String tableHeader = "";
try {
    // create a new file with PrintWriter in a 
    PrintWriter pw = new PrintWriter("output.csv"); 
    File file = new File(inputFileName);
    // Does the file to read exist?
    if (!file.exists()) {
        System.err.println("File Not Found!\n");
        System.exit(0);
    }   
    // create a new scanner object to read file
    scan = new Scanner(file);
    // for each line data
    String line = "";
    tableHeader = scan.nextLine();
    String newline = System.getProperty("line.separator");
    // Print the Table Header to our new file.
    pw.print(tableHeader + newline);

    while (scan.hasNextLine()) {
        line = scan.nextLine();
        // Make sure we don't deal with a blank line.
        if (line.equals("") || line.isEmpty()) {
            continue;
        }
        // split line data into a String Array.
        // Not sure if there is a space after 
        // comma delimiter or not but I'm guessing
        // there is. If not then remove the space.
        String result[] = line.split(", ");
        // variables to create a Stock object
        String timestamp = "";
        double close = 0.0;
        double high = 0.0;
        double low = 0.0;
        double open = 0.0;
        int volume = 0;

        // Make sure there are enough array elements 
        // from our split string to fullfil all our 
        // variables. Maybe some data is missing.
        int resLen = result.length;
        if (resLen > 0) {
            if (resLen >= 1) { timestamp = result[0]; }
            if (resLen >= 2) { close = Double.parseDouble(result[1]); }
            if (resLen >= 3) { high = Double.parseDouble(result[2]); }
            if (resLen >= 4) { low = Double.parseDouble(result[3]); }
            if (resLen >= 5) { open = Double.parseDouble(result[4]); }
            if (resLen >= 6) { volume = Integer.parseInt(result[5]); }
        }
        // store data into ArrayList.
        // Convert the result Array to a decent readable string.
        String resString = Arrays.toString(result).replace("[", "").replace("]", "");
        list.add(resString);
        // Print the string to our output.csv file.
        pw.print(resString + System.getProperty("line.separator"));

        //Stock stock = new Stock(timestamp, close, high, low, open, volume);
    }   
    //close file
    scan.close();
    pw.close();
} 
catch (IOException ex ){
    System.err.println("Can Not Read File!\n" + ex.getMessage() + "\n");
    System.exit(0);
}

// Example to show that the ArrayList actually 
// contains something....
// Print data to Console Window.
tableHeader = tableHeader.replace(" | ", "\t");
tableHeader = "\n" + tableHeader.substring(0, 10) + "\t" + tableHeader.substring(10);
System.out.println(tableHeader);
for (int i = 0; i < list.size(); i++) {
    System.out.println(list.get(i).replace(", ", "\t"));
}