Trouble printing a multiple-line String with PrintWriter into a File

Question

I'm trying to print a multiple-line String into a PrintWriter, but it doesn't recognizes the different lines.

I have this String: "2\n0 0 1 string1\n0 2 1 string2".

The text I expected to have into the file was:

2
0 0 1 string1
0 2 1 string2

but it actually is:

20 0 1 string10 2 1string2

My code is:

 public void save(String str){
    try{
        PrintWriter out = new PrintWriter("file.txt");
        out.println(str);
        out.close();
        System.out.print(str);
    }catch(Exception e){System.out.println(e);}
}

It's printed OK in the console.

I'm using BlueJ to code. My OS is W7 and I just opened the file with notepad.

SOLVED!

Using "\r\n" instead of just "\n" works properly!

How do you look at the file contents? What OS are you using? Are you aware that different OS's consider different characters as new line delimiters? — Sotirios Delimanolis, Jun 25 '14 at 01:29
What platform are you using, and what editor are you looking at the file with, when you see `20 0 1 string10 2 1string2` ? — Dawood ibn Kareem, Jun 25 '14 at 01:29
I weren't aware about different OS's use different delimeters, but I always used "\n" with w7 and it worked well. I opened the text file with notepad and I use Bluej to code. — Joan, Jun 25 '14 at 01:32
Also, on windows the standard delimiter is `\r\n`, in other words `CR LF`. — merlin2011, Jun 25 '14 at 01:33
See http://stackoverflow.com/questions/207947/java-how-do-i-get-a-platform-independent-new-line-character — caskey, Jun 25 '14 at 01:37

score 3 · Answer 1 · edited May 23 '17 at 12:10

3

If you want represent literal newlines on Windows, you need to use \r\n, which is the standard delimiter for that platform.

In other words, your original string needs to be

"2\r\n0 0 1 string1\r\n0 2 1 string2"

However, this quickly becomes non-portable, so you should instead query for the standard delimiter first and then use it to construct your string.

String d = System.getProperty("line.separator");
String mystr = String.format("2%s0 0 1 string1%s0 2 1 string2", d, d)

Moreover, based on this answer, we can use %n format specifier to avoid the call to getProperty().

String mystr = String.format("2%n0 0 1 string1%n0 2 1 string2")

edited May 23 '17 at 12:10

Community

1
1

answered Jun 25 '14 at 01:37

merlin2011

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Shouldn't that be `%n`, not `%%n` on the last two lines? So `String.format("2%n0 0 1 string1%n0 2 1 string2")` with no need for `d` any more? – Dawood ibn Kareem Jun 25 '14 at 02:28
@davidwallace I grabbed that from the linked question. I'll update later if I test and it's wrong. I removed the d though. – merlin2011 Jun 25 '14 at 02:33
Yeah, the answer you took that from says "use `%n`". It seems you misread it. – Dawood ibn Kareem Jun 25 '14 at 03:10
@DavidWallace, I just got to my computer and tested it and you are correct. My answer has now been edited with the correction. It appears that I misread the example in the answer. – merlin2011 Jun 25 '14 at 03:56

score 1 · Answer 2 · answered Jun 25 '14 at 01:36

1

From the PrintWriter.println() javadoc,

Terminates the current line by writing the line separator string. The line separator string is defined by the system property line.separator, and is not necessarily a single newline character ('\n').

So, I think you could use -

try{
  PrintWriter out = new PrintWriter("file.txt");
  for (String s : str.split("\n")) {
    out.println(s);
  }
  out.close();
  System.out.print(str);
}catch(Exception e){System.out.println(e);}

answered Jun 25 '14 at 01:36

Elliott Frisch

198,278
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2

@JoanPuicgerver: Please consider that `\r\n` is only the proper line terminator for windows. Do not needlessly introduce OS dependencies. – Deduplicator Jun 25 '14 at 01:42

Trouble printing a multiple-line String with PrintWriter into a File

2 Answers2