Java BufferedWriter can't write certain characters

Question

I decided to do a test for how many different characters I could write. I tried this code:

for (int i = 0;i < 255;i++) {
    myBufferedWriter.write(i);
}

But in the file, using my hex editor, I saw it counted normally at first 01, 02, 03..., but then it got to 3F, and wrote that around 20 times, and then continued writing normally. Can I not write certain characters? I want to be able to write all characters 0-255.

Full code:

public class Main {
    public static void main(String[] args) {
        try{
            BufferedWriter bw = new BufferedWriter(new FileWriter(new File("abc.txt")));
            for (int i = 0;i < 255;i++) {
                bw.write(i);
            }
            bw.close();
          }catch(Exception e){}
    }
}

@jlordo It does that in any editor. I tried two others. If it was showing the wrong things, then it wouldn't be an hex editor. — Susan Yanders, Jul 04 '13 at 23:33
oh-oh. I didn't look close enough. I have the same output as you. I'll do some research and post an answer. — jlordo, Jul 04 '13 at 23:35
No need to put the answer into the question ... especially since it is not necessarily the best answer. I edited it out. — Stephen C, Jul 05 '13 at 01:35

Stephen C · Answer 1 · 2013-08-14T23:46:13.607

I think your problem is that you are using the wrong API. What is happening with your current code is that your "characters" are being treated as text and encoded using the default character encoding for your platform.

If you want to write data in binary form (e.g. the bytes zero through 255) then you should be using the OutputStream APIs. Specifically BufferedOutputStream.

For example:

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedOutputStream bos = new BufferedOutputStream(
                new FileOutputStream(new File("abc.dat")));
        for (int i = 0; i < 255; i++) {
            bos.write(i);
        }
        bos.close();
    }
}

If you want to be able to write other data types too (in binary form), then DataOutputStream is more appropriate ... because it has a bunch of other methods for writing primitive types and so on. However, if you want to write efficiently you need a BufferedOutputStream in between the FileOutputStream and the DataOutputStream.

How do I write to a file using an output stream? – Susan Yanders Jul 04 '13 at 23:30 — Susan Yanders, Jul 04 '13 at 23:30
@SusanYanders `OutputStream.write()`. +1 for this answer. – user207421 Jul 05 '13 at 00:54 — user207421, Jul 05 '13 at 00:54

score 0 · Answer 2 · answered Jul 04 '13 at 23:51

0

I figured it out. My new code:

public class Main {
    public static void main(String[] args) {
        try{
            DataOutputStream dos = new DataOutputStream(new FileOutputStream(new File("abc.txt")));
            for (int i = 0;i < 255;i++)
                dos.writeByte(i);
            dos.close();
        }catch(Exception e){}
    }
}

answered Jul 04 '13 at 23:51

Susan Yanders

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There are two problems with this code: 1) You aren't doing any buffering so each byte written will do a system call. 2) You are squashing all exceptions - BAD IDEA. – Stephen C Jul 05 '13 at 01:33
@StephenC I know about that. right now it isnt important. And in c++ you can hardly use exceptions anyways – Susan Yanders Jul 05 '13 at 02:27
It is only unimportant if you don't have any bugs that might throw exceptions. If there are bugs, then your code will *silently erase any evidence*. I don't think this should ever be dismissed as unimportant ... unless you are one of those rare people who actually enjoys tracking down obscure bugs. – Stephen C Jul 05 '13 at 03:43

Java BufferedWriter can't write certain characters

2 Answers2