在Java中，我需要读取一个文本文件并将每一行放在单独的数组中。 但是每次阅读文本文件时，我都无法分开

Question

In Java I need to read a text file(the file contains three lines and I need to put each line in a double arrray). But I cant split the line. This is the code I have so far. But I don't know how to proceed:

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;

public class FedEx {
    public static void main(String[] args) throws Exception 
    {
        //Read the file
        FileReader file = new FileReader("info.txt");
        BufferedReader br = new BufferedReader(file);

        String text = " ";
        String line = br.readLine();

        while(line != null)
        {
            text += line;
            line = br.readLine();
        }
        //Print the text file.
        System.out.println(text);
    }
}

Answer 1

I think you want t read a file of numbers and put it inside Array of doubles, If that so you can see this code:

Note: I have used try-with-resource to prevent source leaks.

public class FedEx {

    public static void main(String[] args) throws Exception {
        // Read the file
        try (BufferedReader br = new BufferedReader(new FileReader("info.txt"))) {
            String line;
            List<Double> doubles = new ArrayList<>();
            while ((line = br.readLine()) != null) {
                doubles.add(Double.parseDouble(line));
            }
            System.out.println(doubles);
        }

    }
}

File Sample:

343
6787
19
22
58
0

Output Sample:

[343.0, 6787.0, 19.0, 22.0, 58.0, 0.0]

---

There is no need to add text together, So if you want to just display the content of the file line-by-line, try this:

public class FedEx {
    public static void main(String[] args) throws Exception {
        // Read the file
        try (BufferedReader br = new BufferedReader(new FileReader("info.txt"))) {
            String line;
            while ((line = br.readLine()) != null) {
                System.out.println(line);
            }

        }

    }
}

File Sample:

343
6787
19
22
58
0

Output Sample:

343
6787
19
22
58
0

Answer 2

Here is how you can do this using Java 8 features:

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class FileLineByLine {

    private static List<Double> file2doubles(String fileName) throws IOException {
        try (Stream<String> stream = Files.lines(Paths.get(fileName))) {
            return stream.map(Double::parseDouble).collect(Collectors.toList());
        }
    }


    public static void main(String args[]) throws Exception {

        List<Double> doubles = file2doubles(args[0]);

        System.out.println(doubles);
    }
}

You can make this a bit more general by parameterizing the line transformation, see here https://gist.github.com/sorokod/818ccd65cad967cdecb7dbf4006e4fa0