Java传递字符串数组

Question

I'm pretty new to Java and I'm doing some things for practice. I'm just messing with simple IO stuff right now, reading from a file and then printing to an output. I also played with removing commas from the input and got that part working. My problem is when I try to print the values in my array into a new file. Is the fact that my array is created inside the while loop for the BufferedReader? How can I get the values in the array values to be seen by the BufferedWriter? I'm also curious how I would go about reversing the order of the array when printing to the output file? Thanks for any help guys, I've searched but haven't been able to come across anything this specific.

Code:

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.io.FileWriter;

public class Main {

    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new FileReader("myImport.txt"));
        String line = null;

        while ((line = br.readLine()) != null) {
            String[] values = line.split(",");
            System.out.println("Your file has been evaluated, here are the contents:");
            for (String str : values) {
                System.out.println(str);
            }
        }
        br.close();

        try {

            File file = new File("myOutput.txt");

            // if file doesnt exists, then create it
            if (!file.exists()) {
                file.createNewFile();
            }

            FileWriter fw = new FileWriter(file.getAbsoluteFile());
            BufferedWriter bw = new BufferedWriter(fw);
            bw.write(values);
            for (int i = 0; i < values.length; i++) {
                fw.write(values[i] + "\n");
            }
            bw.close();

            System.out.println("Done");

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

Answer 1

The easiest way to make your array visible to the writer is to declare it before setting it.

String line = null;
String[] values = null;

Then inside your while loop, you instantiate it.

values = line.split(",");

That way it is visible to the writer.

Answer 2

To access your values array you have to declar it as a class member or at the top of the function:

public class Main {
   String[] values;
}

Answer 3

You would either need to add values in a list and iterate through the list, or you could also write as you read from the file.

As the scope of your values is in the while loop reading it, you may choose to write as you print it. That is:

while ((line = br.readLine()) != null) {
    String[] values = line.split(",");
    System.out.println("Your file has been evaluated, here are the contents:");
    for (String str : values) {
        System.out.println(str);
        fw.write(str + "\n");
    }
}

Answer 4

You could simply store an ArrayList and add each split line of the file to that list. Then you can iterate over this list later.

List<String[]> linesList = new ArrayList<>();
while ((line = br.readLine()) != null) {
    String[] values = line.split(",");
    linesList.add(values);
    System.out.println("Your file has been evaluated, here are the contents:");
    for (String str : values) {
        System.out.println(str);
    }
}

Then you can iterate over them later...

for (String[] values : linesList) {
    for (var i = values.length - 1; i >= 0; i--) {
        String value = values[i];
        // Store your value here using your FileWriter, etc.
    }
}