将 .txt 文件中的双精度数读取到列表中

发布于 2024-10-28 14:24:26 字数 1561 浏览 6 评论 0原文

我正在尝试从 .txt 文件中读取双精度值并将它们全部放入列表中。

到目前为止，这是我的代码 ->

（我有一种方法来请求文件并获取数据流，还有一种方法将双精度数放入列表中。）

    public InputFile () throws MyException {
    fileIn = null;
    dataIn = null;
    do {
        filename = JOptionPane.showInputDialog("What is the file called? ");
        try {
            fileIn = new FileInputStream((filename + ".txt"));
            dataIn = new DataInputStream(fileIn);

            return;
        }
            catch (FileNotFoundException e) {
            JOptionPane.showMessageDialog(null, "There is no "+filename + ".txt");
        }
   }
   while (   Question.answerIsYesTo("Do you want to retype the file name")   );
   throw new MyException("No input file was chosen");
}

该部分工作正常。

        public ProcessMain() {
        boolean EOF = false;

    List <Double> allNumbers = new ArrayList <Double> () ;

            try {

                InputFile inputFile = new InputFile();

                        while(EOF == false) {
                        try {
                          allNumbers.add(inputFile.dataIn.readDouble());
                            }
                        catch(EOFException e){ EOF = true; }
                        }

         // List manipulation here. I have no problems with this part.

    }
    catch (Exception e) {
        System.out.println(e);
    }

     System.out.println(allNumbers);

我得到以下信息 -

java.lang.IndexOutOfBoundsException：索引：0，大小：0

有什么想法吗？

原文

I'm trying to read doubles from a .txt file and put them all into a list.

Here's my code so far ->

(I have one method to ask for the file and get the data stream, and one to put the doubles into a list.)

    public InputFile () throws MyException {
    fileIn = null;
    dataIn = null;
    do {
        filename = JOptionPane.showInputDialog("What is the file called? ");
        try {
            fileIn = new FileInputStream((filename + ".txt"));
            dataIn = new DataInputStream(fileIn);

            return;
        }
            catch (FileNotFoundException e) {
            JOptionPane.showMessageDialog(null, "There is no "+filename + ".txt");
        }
   }
   while (   Question.answerIsYesTo("Do you want to retype the file name")   );
   throw new MyException("No input file was chosen");
}

That part works fine.

        public ProcessMain() {
        boolean EOF = false;

    List <Double> allNumbers = new ArrayList <Double> () ;

            try {

                InputFile inputFile = new InputFile();

                        while(EOF == false) {
                        try {
                          allNumbers.add(inputFile.dataIn.readDouble());
                            }
                        catch(EOFException e){ EOF = true; }
                        }

         // List manipulation here. I have no problems with this part.

    }
    catch (Exception e) {
        System.out.println(e);
    }

     System.out.println(allNumbers);

I get the following -

java.lang.IndexOutOfBoundsException: Index: 0, Size: 0

Any ideas?

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情深如许 2024-11-04 14:24:26

DataInputStream 实际上用于读取二进制数据，例如从套接字读取二进制数据。我认为你想要的只是简单的 FileReader ，然后使用 Double.parseDouble(String) 或 Double.valueOf(String) 进行解析 - 取决于无论你想获得原始类型还是对象类型。

如果您的输入文件在新行中包含每个数字，则可以使用 BufferedReader.readLine。否则，您将需要一些简单的解析，例如查找空格或逗号分隔的值。

例如，要读取一个新行中包含每个数字的文件，您可以执行以下操作：

import java.io.*;

public class DoubleReader {
  public static void main(String[] args) throws IOException {
    BufferedReader reader = new BufferedReader(new FileReader(args[0]));
    String line = null;
    while((line = reader.readLine()) != null) {
        Double d = Double.valueOf(line);
        System.err.println(d);
    }
  }
}

但是，如果您的文件以不同的方式分隔数字（例如空格或逗号），您将需要在读取时做一些额外/不同的工作文件来提取（解析）您的值。

解析是关于对数据进行标记，以便您可以提取您感兴趣的位。

DataInputStream is really for reading binary data, e.g. from a socket. I think what you want is just simple FileReader and then parse using Double.parseDouble(String) or Double.valueOf(String) - depending on whether you want to get primitive or Object doubles.

If your input file contains each number on a new line, you can use BufferedReader.readLine. Otherwise you will need some simple parsing, e.g. to find space or comma-separated values.

So for example, to read a file containing each number on a new line you could do something like this:

import java.io.*;

public class DoubleReader {
  public static void main(String[] args) throws IOException {
    BufferedReader reader = new BufferedReader(new FileReader(args[0]));
    String line = null;
    while((line = reader.readLine()) != null) {
        Double d = Double.valueOf(line);
        System.err.println(d);
    }
  }
}

But if your file separates the numbers differently (e.g. space or comma) you will need to do a bit of extra/different work while reading the file to extract (parse) your values.

Parsing is about tokenizing your data so you can extract the bits you're interested in.

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孤独陪着我 2024-11-04 14:24:26

这可能是“EOF = false”行..将“false”分配给“EOF”并且始终为true。尝试将其更改为“EOF == false”。

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゛时过境迁 2024-11-04 14:24:26

DataInputStream 仅用于读取使用相应输出流写入的内容。对于文本文件，请在 FileInputStream 周围创建一个 InputStreamReader（记住指定编码），然后创建一个 BufferedReader，以便您可以通过线。然后使用 Double 类来解析字符串。