CODEWITHSUNDEEP
java
bhxbr922
bhxbr922

Reputation: 47

Numbers in a file

I'm just a beginner and got the following task:

Write first 100 positive and 100 negative integers to the file, listing them separated by a space. Then read this file and put the read numbers into 2 files: positive_numbers and negative_numbers.

public static void main(String[] args) throws IOException {
        File numbers = new File("C:\\numbers.txt");
        File positivNumbers = new File("C:\\positivnumbers.txt");
        File negativNumbers = new File("C:\\negativnumbers.txt");


        try (
                BufferedWriter wr = new BufferedWriter(new FileWriter(numbers));
                BufferedReader rd = new BufferedReader(new FileReader(numbers));
                BufferedWriter brnegativ = new BufferedWriter(new FileWriter(negativNumbers));
                BufferedWriter brpositiv = new BufferedWriter(new FileWriter(positivNumbers));) {

            if (numbers.exists()) {
                for (int i = 0; i <= 100; i++) {
                    wr.write(String.valueOf((i) + " "));
                }
                for (int a = -1; a >= -100; a--) {
                    wr.write(((a) + " "));
                }

                String line = rd.readLine();
                while (line != null) {
                    brpositiv.write(line);
                }

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

I could write numbers as a String to file "numbers". But I cannot read and write them in "positiv" output file.The file is empty. Where is my mistake?

Upvotes: 0

Views: 53

Answers (1)

Conffusion
Conffusion

Reputation: 4475

After the writing you have to close wr so all data in memory gets flushed to the file. AFTER the close you can reopen it for read. So in your code you open rd too soon.

   try (BufferedWriter wr = new BufferedWriter(new FileWriter(numbers));) {
        for (int i = 0; i <= 100; i++) {
            wr.write(String.valueOf((i) + " "));
        }
        for (int a = -1; a >= -100; a--) {
            wr.write(((a) + " "));
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
    // file is closed by try-with-resources ...

    // ... so now we can open it for read:
    try (BufferedReader rd = new BufferedReader(new FileReader(numbers));
         BufferedWriter brnegativ = new BufferedWriter(new FileWriter(negativNumbers));
         BufferedWriter brpositiv = new BufferedWriter(new FileWriter(positivNumbers));) {
            String line = rd.readLine();
            while (line != null) {
                brpositiv.write(line);
               // TODO : split logic
            }
    } catch (IOException e) {
        e.printStackTrace();
    }

Upvotes: 3

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