Java: Blank File on writing

Question

I am trying to write to a file in Java using the following function:

public void writeTextFile(String filename, double s){
  FileWriter output=null;
  try{
    output= new FileWriter(filename);
    BufferedWriter writer=new BufferedWriter(output);
    String ss = String.valueOf(s);
    writer.write(ss);
  } catch (Exception e) {
    throw new RuntimeException(e);
  } finally {
    if (output != null) {
      try {
        output.flush();
        output.close();
      } catch (IOException e) {

      }
    }
  }
}

I also tried using:

FileOutputStream out;
PrintStream prt;
try{
  out= new FileOutputStream("result");
  prt=new PrintStream(out);
  prt.println(value);
  prt.flush();
  prt.close();
}
catch(Exception e){
  System.out.println("File write error");}

But i end up with a blank output file with both the methods. Need help!!:(

What is printed if you add `System.out.println("value: '" + value + "'");`? — Grzegorz Żur, Jun 17 '13 at 09:18

score 2 · Accepted Answer · answered Jun 17 '13 at 09:51

This will work,

public void writeTextFile(String filename, double s){
 FileWriter output=null;
 try{
  output= new FileWriter(filename);
  BufferedWriter writer=new BufferedWriter(output);
  String ss = String.valueOf(s);
  writer.append(ss);
  writer.close();
} catch (Exception e) {
  throw new RuntimeException(e);
} finally {
  if (output != null) {
  try {
    output.flush();
    output.close();
  } catch (IOException e) {

  }
}
}
}

score 1 · Answer 2 · answered Jun 17 '13 at 09:26

Hey its simple the error is that you aren't flushing the bufferedwriter please do that before you flush and close the stream.

add this to your first code

public static void writeTextFile(String filename, double s){
        FileWriter output=null;
        try{
            output= new FileWriter(filename);
            BufferedWriter writer=new BufferedWriter(output);
            String ss = String.valueOf(s);
            System.out.println("ss:"+ss);
            writer.write(ss);
            writer.flush();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (output != null) {
                try {
                    output.flush();
                    output.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

Adding *close()* works. Flush before close is redundant. – user207421 Feb 06 '14 at 02:23 — user207421, Feb 06 '14 at 02:23

dbkoren · Answer 3 · 2013-06-17T09:25:49.927

0

try this

use this link : Tutorial on file writing

Code from the link :

public static void main(String[] args) {
        try {

            String content = "This is the content to write into file";

            File file = new File("/users/mkyong/filename.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(content);
            bw.close();

            System.out.println("Done");

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

edited Jun 17 '13 at 09:25

answered Jun 17 '13 at 09:19

dbkoren

1,305
1
11
16

There's nothing wrong with instantiating a `FileWriter` directly using the filename. Using `File` is not necessary. – Rajesh J Advani Jun 17 '13 at 09:22
you are correct , its another option not necessary ... Edited. – dbkoren Jun 17 '13 at 09:26
You don't need to call createNewFile(). Poor quality tutorial. – user207421 Feb 06 '14 at 02:22

score -2 · Answer 4 · answered Jun 17 '13 at 09:18

-2

What if you try:

File file = new File("c:/newfile.txt");
    String content = "This is the text content";

    try (FileOutputStream fop = new FileOutputStream(file)) {

        // if file doesn't exists, then create it
        if (!file.exists()) {
            file.createNewFile();
        }

        // get the content in bytes
        byte[] contentInBytes = content.getBytes();

        fop.write(contentInBytes);
        fop.flush();
        fop.close();

        System.out.println("Done");

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

Based on this tutorial: http://www.mkyong.com/java/how-to-write-to-file-in-java-fileoutputstream-example/

answered Jun 17 '13 at 09:18

Enrichman

11,157
11
67
101

You don't need to call createNewFile(), or flush before closing. Poor quality tutorial. – user207421 Feb 06 '14 at 02:21
@EJP no need to downvote, they're just patterns (it's not a poor qualit tutorial). Read here http://stackoverflow.com/questions/9620683/java-fileoutputstream-create-file-if-not-exists and here http://stackoverflow.com/questions/9858495/using-flush-before-close – Enrichman Feb 06 '14 at 10:06

score -2 · Answer 5 · edited Feb 06 '14 at 02:13

-2

You have to flush and close BufferedWriter not FileWriter.

edited Feb 06 '14 at 02:13

László Papp

51,870
39
111
135

answered Feb 06 '14 at 01:51

Sovanndy

1

3

While this is correct, it's already been said (and accepted) by others. You should only answer if it adds something that someone else hasn't said. – mdewitt Feb 06 '14 at 02:15
And you don't have to flush, only close. – user207421 Feb 06 '14 at 02:23

Java: Blank File on writing

5 Answers5