Develop Reference

Strings act weirdly when reading them from a file with the java.util.Scanner and using linebreaks as delimiter

I try to read data from a file using the java.util.Scanner. When I try to use \n as a delimiter, then the resulting Strings react weirdly when I try to add more text to them.
I have a file called "test.txt" and try to read data from it. I then want to add more text to each String, similar to how this would print Hello World!:
String helloWorld = "Hello "+"World!";
System.out.println(helloWorld);.
I tried combining data with +, I tried += and I tried String.concat(), this has worked for me before and usually still works.
I also tried to use different delimiters, or no delimiter at all, both of those work as I expect, but I need the Strings to be separated at line breaks.
The test.txt file for the minimal reproducible example contains this text (there is a space at the end of each line):
zero:
one:
two:
three:
void minimalReproducibleExample() throws Exception { //May throw an exception if the test.txt file can't be found
String[] data = new String[4];
java.io.File file = new java.io.File("test.txt");
java.util.Scanner scanner = new java.util.Scanner(file).useDelimiter("\n");
for (int i=0;i<4;i++) {
data[i] = scanner.next(); //read the next line
data[i] += i; //add a number at the end of the String
System.out.println(data[i]); //print the String with the number
}
scanner.close();
}
I expect this code to print out these lines:
zero: 0
one: 1
two: 2
three: 3
I get this output instead:
0ero:
1ne:
2wo:
three: 3
Why do I not get the expected output when using \n as a delimiter?

The test.txt is most likely using Windows end of line representation \r\n which results in carriage return \r still being present in the String after it's read.
Ensure that test.txt is using \n as line delimtier or use Windows \r\n in Scanner.useDelimiter().

The problem is most likely with a wrong delimiter. If you use Windows 10, the new line separator is \r\n.
Just to be platform-independent use System.getProperty("line.separator") instead of hardcoded \n.

How to print text on new line using "\n"

I try to create one big String in appropriate format as i want and print it using PrinterJob class. Here is the code of String:
String bigtext = "The name\n" + "some another text";
Graphics2D's_object.drawString(bigtext, 50, 50);
But it prints as "The name some another text" in one line, "\n" does not work, while i want to print "some another text" in another line.
P.S. I try to print bigtext in printer.
SOLVED: Here is the solution: Problems with newline in Graphics2D.drawString. (after long trouble :))

The linefeed character \n is not the line separator in certain operating systems use \r\n. Additionally i would recommend use of StringBuilder rather then using +
Edit : You can use System.getProperty("line.separator"); as well.

A similar question was asked yesterday and this is what helped:
The problem that you are encountering is because of the "line separator" you are hard coding. It's best to get the System's line separator with:
System.getProperty("line.separator");
So that your code would look like this:
String lineseparator=System.getProperty("line.separator");
// I'd suggest putting this as a class variable, so that it only gets called once
// rather than everytime you call the addLine() method
String bigtext = "The name" + lineseparator + "some another text";
//If you wanted an empty line in between them, then add the lineseparator twice
String bigtext = "The name" + lineseparator + lineseparator + "some another text";

It seems most of the guys don't understand the question. I tried the PrinterJob and it doesn't work for me neither.
I found a solution but not verifyied:
How to print strings with line breaks in java

Java Buffere Reader split add string

I am reading a CSV file of 4GB in java what I have to do is extract 100000 record from file and make a separate file but problem is when I am reading a line
line = br.readLine() and String[] record = line.split(cvsSplitBy); it adds one extra "" in every string like when I open a record array it look like
""abc"",""bcd"",""cef"",""dgh"",""elk"" it should be like "abc","bcd","cef","dgh","elk"
Kindly let me know why its adding extra commas against every string

Post your code so we can investigate. In the mean time you can remove those extra "" or do something like:
line.split("\"" + cvsSplitBy + "\"")
Post your code and I'll edit this reply.

Scanner's nextLine(), Only fetching partial

So, using something like:
for (int i = 0; i < files.length; i++) {
if (!files[i].isDirectory() && files[i].canRead()) {
try {
Scanner scan = new Scanner(files[i]);
System.out.println("Generating Categories for " + files[i].toPath());
while (scan.hasNextLine()) {
count++;
String line = scan.nextLine();
System.out.println(" ->" + line);
line = line.split("\t", 2)[1];
System.out.println("!- " + line);
JsonParser parser = new JsonParser();
JsonObject object = parser.parse(line).getAsJsonObject();
Set<Entry<String, JsonElement>> entrySet = object.entrySet();
exploreSet(entrySet);
}
scan.close();
// System.out.println(keyset);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
}
as one goes over a Hadoop output file, one of the JSON objects in the middle is breaking... because scan.nextLine() is not fetching the whole line before it brings it to split. ie, the output is:
->0 {"Flags":"0","transactions":{"totalTransactionAmount":"0","totalQuantitySold":"0"},"listingStatus":"NULL","conditionRollupId":"0","photoDisplayType":"0","title":"NULL","quantityAvailable":"0","viewItemCount":"0","visitCount":"0","itemCountryId":"0","itemAspects":{ ... "sellerSiteId":"0","siteId":"0","pictureUrl":"http://somewhere.com/45/x/AlphaNumeric/$(KGrHqR,!rgF!6n5wJSTBQO-G4k(Ww~~
!- {"Flags":"0","transactions":{"totalTransactionAmount":"0","totalQuantitySold":"0"},"listingStatus":"NULL","conditionRollupId":"0","photoDisplayType":"0","title":"NULL","quantityAvailable":"0","viewItemCount":"0","visitCount":"0","itemCountryId":"0","itemAspects":{ ... "sellerSiteId":"0","siteId":"0","pictureUrl":"http://somewhere.com/45/x/AlphaNumeric/$(KGrHqR,!rgF!6n5wJSTBQO-G4k(Ww~~
Most of the above data has been sanitized (not the URL (for the most part) however... )
and the URL continues as:
$(KGrHqZHJCgFBsO4dC3MBQdC2)Y4Tg~~60_1.JPG?set_id=8800005007
in the file....
So its slightly miffing.
This also is entry #112, and I have had other files parse without errors... but this one is screwing with my mind, mostly because I dont see how scan.nextLine() isnt working...
By debug output, the JSON error is caused by the string not being split properly.
And almost forgot, it also works JUST FINE if I attempt to put the offending line in its own file and parse just that.
EDIT:
Also blows up if I remove the offending line in about the same place.
Attempted with JVM 1.6 and 1.7
Workaround Solution:
BufferedReader scan = new BufferedReader(new FileReader(files[i]));
instead of scanner....

Based on your code, the best explanation I can come up with is that the line really does end after the "~~" according to the criteria used by Scanner.nextLine().
The criteria for an end-of-line are:
Something that matches this regex: "\r\n|[\n\r\u2028\u2029\u0085]" or
The end of the input stream
You say that the file continues after the "~~", so lets put EOF aside, and look at the regex. That will match any of the following:
The usual line separators:
<CR>
<NL>
<CR><NL>
... and three unusual forms of line separator that Scanner also recognizes.
0x0085 is the <NEL> or "next line" control code in the "ISO C1 Control" group
0x2028 is the Unicode "line separator" character
0x2029 is the Unicode "paragraph separator" character
My theory is that you've got one of the "unusual" forms in your input file, and this is not showing up in .... whatever tool it is that you are using to examine the files.
I suggest that you examine the input file using a tool that can show you the actual bytes of the file; e.g. the od utility on a Linux / Unix system. Also, check that this isn't caused by some kind of character encoding mismatch ... or trying to read or write binary data as text.
If these don't help, then the next step should be to run your application using your IDE's Java debugger, and single-step it through the Scanner.hasNextLine() and nextLine() calls to find out what the code is actually doing.
And almost forgot, it also works JUST FINE if I attempt to put the offending line in its own file and parse just that.
That's interesting. But if the tool you are using to extract the line is the same one that is not showing the (hypothesized) unusual line separator, then this evidence is not reliable. The process of extraction may be altering the "stuff" that is causing the problems.

Java: how to write formatted output to plain text file

I am developing a small java application. At some point i am writing some data in a plain text file. Using the following code:
Writer Candidateoutput = null;
File Candidatefile = new File("Candidates.txt"),
Candidateoutput = new BufferedWriter(new FileWriter(Candidatefile));
Candidateoutput.write("\n Write this text on next line");
Candidateoutput.write("\t This is indented text");
Candidateoutput.close();
Now every thing goes fine, the file is created with the expected text. The only problem is that the text was not formatted all the text was on single line. But if I copy and paste the text in MS Word then the text is formatted automatically.
Is there any way to preserver text formatting in Plain text file as well?
Note: By text formatting I am referring to \n and \t only

Use System.getProperty("line.separator") for new lines - this is the platform-independent way of getting the new-line separator. (on windows it is \r\n, on linux it's \n)
Also, if this is going to be run on non-windows machines, avoid using \t - use X (four) spaces instead.

You can use line.separator system property to solve your issue.
E.g.
String separator = System.getProperty("line.separator");
Writer Candidateoutput = null;
File Candidatefile = new File("Candidates.txt"),
Candidateoutput = new BufferedWriter(new FileWriter(Candidatefile));
Candidateoutput.write(separator + " Write this text on next line");
Candidateoutput.write("\t This is indented text");
Candidateoutput.close();
line.separator system property is a platform independent way of getting a newline from your environment.

A PrintWriter does this platform independent - use the println() methods.

You would have to use the Java utility Formatter which can be found here: java.util.Formatter
Then all you would have to do is create an object of Formatter type such as this:
private Formatter output;
In this case, output will be the output file you are writing to.
Then you have to pass the file name to the output object like this:
output = new Formatter("name.of.your.file.txt")
Once that's done, you can either hard-code the file contents to your output file using the output.format command which is similar to the System.out.println or printf commands.
Or use the Scanner utility to input the data into memory then use output.format to output this data to the output object or file.
This is an example on how to write a record to output:
output.format( "%d %s %s %2f\n" , field1.decimal, field2.string, field3.string, field4.double)
There is a little bit more to it than this, but this sure beats parsing data, or using a bunch of complicated third party plugins.
To read this file you would redirect the Scanner utility to read a file instead of the console:
input = new Scanner(new File( "name.of.your.file.txt")

Window's Notepad needs \r\n to display a new-line correctly. Only \n is ignored by Notepad.

Well Windows expects a newline and a carriage return char to indicate a new line. So you'd want to do \r\n to make it work.