Thread: Need help with BufferedReader and BufferedWriter

So given an input file, input.txt. I am trying to write a program that will firstly: print each line from input.txt line by line as it appears in the text file. So lets say the text file says:

This line first
This line seccond

Then when I print it should say:

This line first
This line seccond

Secondly, I want to print such that the input text reads:

This
line
first
This
line
seccond

Thirdly, I want to write to a file such that the output matches the input. So again if the input is:

This line first
This line seccond

Then the output file (outputTextA in this case) should read:

This line first
This line seccond

Here is my code for doing those first three steps and it works just fine:

String inputFile = "src/input/input.txt";
        String outputFileA = "src/output/outputA.txt";
        String outputFileB = "src/output/outputB.txt";
        StringBuilder outputStringA = new StringBuilder();
 
        try (BufferedReader reader = new BufferedReader(new FileReader(inputFile))){
 
            String line;
 
            while ((line = reader.readLine()) != null){
 
                outputStringA.append(line);
 
                if (line != null){
                    outputStringA.append(System.lineSeparator());
                }
            }
 
            System.out.println(outputStringA);
 
        }catch(IOException x){
            System.err.format("IOException: %s%n", x);
        }
 
        String s1 = outputStringA.toString();
 
        for (String word : s1.split(" ")){
 
            System.out.println(word);
        }
 
        try (BufferedWriter writer = new BufferedWriter(new FileWriter(outputFileA))){
 
            writer.write(s1, 0, outputStringA.length());
        }catch(IOException x){
            System.err.format("IOException: %s%n", x);
        }

Now, I want to output to a file such that if the input text is:

This line first
This line seccond

Then the output text would be:

This
line
first
This
line
seccond

However, I cannot figure out how!

I have tried many things none of which are working. I have tried:

for (String word : s1.split(" ")) {
 
            try (BufferedWriter writer = new BufferedWriter(new FileWriter(outputFileB))) {
 
                writer.write(word, 0, outputStringA.length());
            } catch (IOException x) {
                System.err.format("IOException: %s%n", x);
            }
        }

However this throws and exception. I have also tried:

try (BufferedWriter writer = new BufferedWriter(new FileWriter(outputFileA))) {
            for (String word : s1.split(" ")) {
                writer.write(word, 0, outputStringA.length());
 
            }
        } catch (IOException x) {
            System.err.format("IOException: %s%n", x);
        }

However, this also throws and exception.

There must be an easier way can someone please help me out?

--- Update ---

Just a quick note I also tried converting the string s1 into an array list. Then tried writting the array list to the file like this:

List<String> myList = new ArrayList<String>(Arrays.asList(s1.split(" ")));

Then although I was able to write the list into the file I could not figure out how to write the list into the file in the proper format.

Well I can split the string up into tokens separated by spaces. However, I can't seem to figure out how to then take each of those tokens and write them to a file. For instance, if the input file reads:

This is a line
another line

Then I have figured out how to print in the console such that it prints each word in a new line using the split method like this:

This
is
a
line
another
line

However, I can't seem to figure out how to write that same format to a file.

--- Update ---

The solution to me seems pretty simple. Just split it up in a loop and write each word to the file on a new line. However, when I try to do that the program throws an exception.

Okay here's my program as I think it should work:

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package lab1;
 
import java.io.*;
import java.util.Arrays;
 
/**
 *
 * @author vysero
 */
public class Lab1 {
 
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
 
        String inputFile = "src/input/input.txt";
        String outputFileA = "src/output/outputA.txt";
        String outputFileB = "src/output/outputB.txt";
        StringBuilder outputStringA = new StringBuilder();
 
        try (BufferedReader reader = new BufferedReader(new FileReader(inputFile))) {
 
            String line;
 
            while ((line = reader.readLine()) != null) {
 
                outputStringA.append(line);
 
                if (line != null) {
                    outputStringA.append(System.lineSeparator());
                }
            }
 
            System.out.println(outputStringA);
 
        } catch (IOException x) {
            System.err.format("IOException: %s%n", x);
        }
 
        String s1 = outputStringA.toString();
 
        for (String word : s1.split(" ")) {
 
            System.out.println(word);
        }
 
        try (BufferedWriter writer = new BufferedWriter(new FileWriter(outputFileA))){
 
            writer.write(s1, 0, outputStringA.length());
 
        } catch (IOException x) {
            System.err.format("IOException: %s%n", x);
        }
 
        try (BufferedWriter writer = new BufferedWriter(new FileWriter(outputFileB))){
 
            for(String newS : s1.split(" ")){
 
                writer.write(newS, 0, outputStringA.length());
            }
        } catch (IOException x) {
            System.err.format("IOException: %s%n", x);
        }
    }
}

Here is the error it throws:

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 424
at java.lang.String.getChars(String.java:809)
at java.io.BufferedWriter.write(BufferedWriter.java:2 26)
at lab1.Lab1.main(Lab1.java:65)
Java Result: 1

Originally Posted by Norm

The code at line 65 used and index (424) past the end of the String.

What is that line trying to do? What are the values being passed to the write method?

Please read the API doc for the write() method to see what args it takes.

You Sr. are a genius, thank you!