Develop Reference

Keep new lines when reading in a file

I'm trying to read in a file and modify the text, but I need to keep new lines when doing so. For example, if I were to read in a file that contained:
This is some text.
This is some more text.
It would just read in as
This is some text.This is some more text.
How do I keep that space? I think it has something to do with the /n escape character. I've seen using BufferReader and FileReader, but we haven't learned that in my class yet, so is there another way? What I've tried is something like this:
if (ch == 10)
{
ch = '\n';
fileOut.print(ch);
}
10 is the ASCII table code for a new line, so I thought Java could recognize it as that, but it doesn't.

In Java 8:
You can read lines using:
List<String> yourFileLines = Files.readAllLines(Paths.get("your_file"));
Then collect strings:
String collect = yourFileLines.stream().filter(StringUtils::isNotBlank).collect(Collectors.joining(" "));

The problem is that you (possibly) want to read your file a line at a time, and then you want to write it back a line at a time (keeping empty lines).
The following source does that, it reads the input file one line at a time, and writes it back one line at a time (keeping empty lines).
The only problem is ... it possibly changes the new line, maybe you are reading a unix file and write a dos file or vice-versa depending on the system you are running in and the source type of the file you a reading.
Keeping the original newline can introduce a lot complexity, read BufferedReader and PrintWriter api docs for more information.
public void process(File input , File output){
try(InputStream in = new FileInputStream(input);
OutputStream out = new FileOutputStream(output)){
BufferedReader reader = new BufferedReader(new InputStreamReader(in, "utf-8"),true);
PrintWriter writer = new PrintWriter( new OutputStreamWriter(out,"utf-8"));
String line=null;
while((line=reader.readLine())!=null){
String processed = proces(line);
writer.println(processed);
}
} catch (IOException e) {
// Some exception management
}
}
public String proces(String line){
return line;
}

/n should be \n
if (ch == 10)
{
ch = '\n';
fileOut.print(ch);
}

Is that a typo?
ch = '/n';
otherwise use
ch = '\n';

Java replace line in a text file

I found this code from another question
private void updateLine(String toUpdate, String updated) throws IOException {
BufferedReader file = new BufferedReader(new FileReader(data));
String line;
String input = "";
while ((line = file.readLine()) != null)
input += line + "\n";
input = input.replace(toUpdate, updated);
FileOutputStream os = new FileOutputStream(data);
os.write(input.getBytes());
file.close();
os.close();
}
This is my file before I replace some lines
example1
example2
example3
But when I replace a line, the file now looks like this
example1example2example3
Which makes it impossible to read the file when there are a lot of lines in it.
How would I go about editing the code above to make my file look what it looked like at the start?

Use System.lineSeparator() instead of \n.
while ((line = file.readLine()) != null)
input += line + System.lineSeparator();
The issue is that on Unix systems, the line separator is \n while on Windows systems, it's \r\n.
In Java versions older then Java 7, you would have to use System.getProperty("line.separator") instead.
As pointed out in the comments, if you have concerns about memory usage, it would be wise to not store the entire output in a variable, but write it out line-by-line in the loop that you're using to process the input.

If you read and modify line by line this has the advantage, that you dont need to fit the whole file in memory. Not sure if this is possible in your case, but it is generally a good thing to aim for streaming. In your case this would in addition remove the need for concatenate the string and you don't need to select a line terminator, because you can write each single transformed line with println(). It requires to write to a different file, which is generally a good thing as it is crash safe. You would lose data if you rewrite a file and get aborted.
private void updateLine(String toUpdate, String updated) throws IOException {
BufferedReader file = new BufferedReader(new FileReader(data));
PrintWriter writer = new PrintWriter(new File(data+".out"), "UTF-8");
String line;
while ((line = file.readLine()) != null)
{
line = line.replace(toUpdate, updated);
writer.println(line);
}
file.close();
if (writer.checkError())
throw new IOException("cannot write");
writer.close();
}
In this case, it assumes that you need to do the replace only on complete lines, not multiple lines. I also added an explicit encoding and use a writer, as you have a string to output.

This is because you use OutputStream which is better for handling binary data. Try using PrintWriter and don't add any line terminator at the end of the lines. Example is here

new line is missing while writing file using NIO

i am trying to copy the content of one file to new file and somehow new line are missing in the new file and its created as one row, i guess its related to buffer position.
following the code that i am using..
List<String> lines;
FileChannel destination = null;
try
{
lines = Files.readAllLines(Paths.get(sourceFile.getAbsolutePath()), Charset.defaultCharset());
destination = new FileOutputStream(destFile).getChannel();
ByteBuffer buf = ByteBuffer.allocate(1024);
for (String line : lines)
{
System.out.println(line);
buf.clear();
buf.put(line.getBytes());
buf.flip();
while (buf.hasRemaining())
{
destination.write(buf);
}
}
}
finally
{
if (destination != null)
{
destination.close();
}
}

Do buff.put(System.getProperty("line.separator").toString()); before buf.put(line.getBytes());

The line where you're writing the bytes:
buf.put(line.getBytes());
...doesn't include the new line character, you're just writing the bytes of each individual line. You need to write the new line character separately after each instance.

You might prefer to use Java 7's Files.copy:
Files.copy(sourceFile.toPath(), destinationFile.toPath(),
StandardCopyOption.REPLACE_EXISTING);
One should once write a file copy oneself.
However your current version uses the default platform encoding to read the file as text. This goes wrong on UTF-8 (some illegal multibyte sequences), on the \u0000 nul char, converts the line endings to the default platform ones.

This will include the new line:
ByteBuffer bf = null;
final String newLine = System.getProperty("line.separator");
bf = ByteBuffer.wrap((yourString+newLine).getBytes(Charset.forName("UTF-8" )));

You can directly use System.lineSeparator() insted of System.getProperty("line.separator")
buff.put(System.lineSeparator().toString());

Java read file with strings from different languages

I made a program that reads different text files and combines this into a .csv file. Its a .csv file with translations into English, dutch, french, italian, portuguese and spanish.
Now here is my problem:
In the end i get a nice filled .csv file with all the translations together. I read the files with UTF-8 and all the languages get shown right except for the french one. Some chars are shows as Questionmarks like these: "Mis ? jour" and it should be "Mis à jour".
Here is the method that reads the different files with the different languages and makes objects from them so i can sort them en put them in the right spot in the .csv file
The files are filled like this:
To Airport;A l’aéroport
Today;Aujourd’hui
public static Language getTranslations(String inputFileName) {
Language language = new Language();
FileInputStream fstream;
try {
fstream = new FileInputStream(inputFileName);
// Get the object of DataInputStream
DataInputStream in = new DataInputStream(fstream);
BufferedReader br = new BufferedReader( new InputStreamReader( new FileInputStream(inputFileName), "UTF-8"));
String strLine;
//Read File Line By Line
while ((strLine = br.readLine()) != null) {
// Print the content on the console
String[] values = strLine.split(";");
if(values.length == 2) {
language.putTranslationItem(values[0], values[1]);
}
}
//Close the input stream
in.close();
} catch (FileNotFoundException e) {
} catch (IOException e) {
}
return language;
}
I hope anybody can help out!
Thanks

I am not completely sure about this , but you can try to convert the values[0] and values[1] strings into bytearray
byte[] value_0_utfString = values[0].getBytes("UTF-8") ;
byte[] value_1_utfString = values[1].getBytes("UTF-8") ;
and then convert it back into a string
str_0 = new String(value_0_utfString ,"UTF-8") ;
str_1 = new String(value_1_utfString ,"UTF-8") ;
Not sure if this is the right / optimized way , but since a single line comprises of both english and french , I thought splitting and encoding might help , I haven't tried this myself

Resave the text file by clicking "save as" in any text editor(eg: memopad) and change the encoding type to ANSI instead of UTF-8.

Java save multiline string to text file

I am new to Java and trying to save a multi line string to a text file.
Right now, it does work within my application. Like, if I save the file from my application and then open it from my application, it does put a space between lines. However, if I save the file from my app and then open it in Notepad, it is all on one line.
Is there a way to make it show multi line on all programs? Here's my current code:
public static void saveFile(String contents) {
// Get where the person wants to save the file
JFileChooser fc = new JFileChooser();
int rval = fc.showSaveDialog(fc);
if(rval == JFileChooser.APPROVE_OPTION) {
File file = fc.getSelectedFile();
try {
//File out_file = new File(file);
BufferedWriter out = new BufferedWriter(new FileWriter(file));
out.write(contents);
out.flush();
out.close();
} catch(IOException e) {
messageUtilities.errorMessage("There was an error saving your file. IOException was thrown.", "File Error");
}
}
else {
// Do nothing
System.out.println("The user choose not to save anything");
}
}

depending on how you are constructing your string, you may just be running into a line ending problem. Notepad does not support unix line endings (\n only) it only supports windows line endings (\n\r). try opening your saved file using a more robust editor, and/or make sure you are using the proper line endings for your platform. java's system property (System.getProperty("line.separator")) will get you the proper line ending for the platform that the code is running on.
while you're building your string to be saved to the file, rather than explicitly specifying "\n" or "\n\r" (or on the mac "\r") for your line endings, you would instead append the value of that system property.
like so:
String eol = System.getProperty("line.separator");
... somewhere else in your code ...
String texttosave = "Here is a line of text." + eol;
... more code.. optionally adding lines of text .....
// call your save file method
saveFile(texttosave);

Yea as the previous answer mentions the System.getProperty("line.seperator").
your code doesn't show how you created String contents but since you said you were new to java I thought i'd mention that in java concatenating Strings is not nice since it creates a. If you are building the String by doing this:
String contents = ""
contents = contents + "sometext" + "some more text\n"
Then consider using java.lang.StrinBuilder instead
StringBuilder strBuilder = new StringBuilder();
strBuilder.append("sometext").append("somre more text\n");
...
String contents = strBuilder.toString();
Another alternative is to stream what ever your planning to write to a file rather than building a large string and then outputting that.

You could add something like:
contents = contents.replaceAll("\\n","\\n\\r");
if notepad does not display correctly. However you might run into a different problem: at each save/load you will get multiple \r chars. Then to avoid that at load you would have to call the same code above but with reversed parameters. This is really an ugly solution just to get the text to display properly in notepad.

I had this same problem my guy friend, after much thought and research I even found a solution.
You can use the ArrayList to put all the contents of the TextArea for exemple, and send as parameter by calling the save, as the writer just wrote string lines, then we use the "for" line by line to write our ArrayList in the end we will be content TextArea in txt file.
if something does not make sense, I'm sorry is google translator and I who do not speak English.
Watch the Windows Notepad, it does not always jump lines, and shows all in one line, use Wordpad ok.
private void SaveActionPerformed(java.awt.event.ActionEvent evt) {
String NameFile = Name.getText();
ArrayList< String > Text = new ArrayList< String >();
Text.add(TextArea.getText());
SaveFile(NameFile, Text);
}
public void SaveFile(String name, ArrayList< String> message) {
path = "C:\\Users\\Paulo Brito\\Desktop\\" + name + ".txt";
File file1 = new File(path);
try {
if (!file1.exists()) {
file1.createNewFile();
}
File[] files = file1.listFiles();
FileWriter fw = new FileWriter(file1, true);
BufferedWriter bw = new BufferedWriter(fw);
for (int i = 0; i < message.size(); i++) {
bw.write(message.get(i));
bw.newLine();
}
bw.close();
fw.close();
FileReader fr = new FileReader(file1);
BufferedReader br = new BufferedReader(fr);
fw = new FileWriter(file1, true);
bw = new BufferedWriter(fw);
while (br.ready()) {
String line = br.readLine();
System.out.println(line);
bw.write(line);
bw.newLine();
}
br.close();
fr.close();
} catch (IOException ex) {
ex.printStackTrace();
JOptionPane.showMessageDialog(null, "Error in" + ex);
}