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How to read every second line from a file in java

Can someone tell me how to read every second line from a file in java?
BufferedReader br = new BufferedReader(new FileReader(file));
String line = br.readLine();
while(line != null){
//Do something ..
line = br.readLine()
}
br.close

One simple way would be to just maintain a counter of number of lines read:
int count = 0;
String line;
while ((line = br.readLine()) != null) {
if (count % 2 == 0) {
// do something with this line
}
++count;
}
But this still technically reads every line in the file, only choosing to process every other line. If you really only want to read every second line, then something like RandomAccessFile might be necessary.

You can do it in Java 8 fashion with very few lines :
static final int FIRST_LINE = 1;
Stream<String> lines = Files.lines(path);
String secondLine = lines.limit(2).skip(FIST_LINE).collect(Collectors.joining("\n"));
First you stream your file lines
You keep only the two first lines
Skip the first line
Note : In java 8, when using Files.lines(), you are supposed to close the stream afterwards or use it in a try-with-resource block.

This is similar to #Tim Biegeleisen's approach, but I thought I would show an alternative to get every other line using a boolean instead of a counter:
boolean skipOddLine = true;
String line;
while ((line = br.readLine()) != null) {
if (skipOddLine = !skipOddLine) {
//Use the String line here
}
}
This will toggle the boolean value every loop iteration, skipping every odd line. If you want to skip every even line instead you just need to change the initial condition to boolean skipOddLine = false;.
Note: This approach only works if you do not need to extend functionality to skip every 3rd line for example, where an approach like Tim's would be easier to modify. It also has the downside of being harder to read than the modulo approach.

This will help you to do it very well
You can use try with resource
You can use stream api java 8
You can use stream api supplier to use stream object again and again
I already hane added comment area to understand you
try (BufferedReader reader =
new BufferedReader(
new InputStreamReader(
new ByteArrayInputStream(x.getBytes()),
"UTF-8"))) { //this will help to you for various languages reading files
Supplier<Stream<String>> fileContentStream = reader::lines; // this will help you to use stream object again and again
if (FilenameUtils.getExtension(x.getOriginalFilename()).equals("txt")) { this will help you to various files extension filter
String secondLine = lines.limit(2).skip(FIST_LINE).collect(Collectors.joining("\n"));
String secondLine =
fileContentStream
.get()
.limit(2)
.skip(1)// you can skip any line with this action
.collect(Collectors.joining("\n"));
}
else if (FilenameUtils.getExtension(x.getOriginalFilename()).equals("pdf")) {
} catch (Exception ex) {
}

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';

Reading every 10 lines using a BufferedReader

Is there a way of reading, say, every 10 lines from a .txt file using a BufferedReader? At the moment my BufferedReader is reading every line, splitting the different values and storing them in an array list; which is then used elsewhere in my program.

Use LineNumberReader which is intended for this very purpose:
LineNumberReader reader = new LineNumberReader(fileReader);
ArrayList<String> goodLines = new ArrayList<String>();
String line = null;
while ((line = reader.readLine()) != null) {
if ((reader.getLineNumber()+1) % 10 == 0) {
goodLines.add(line);
}
}

Use a loop to read all the lines you don't want, then read the line you do want.
BufferedReader br = new BufferedReader(new FileReader(file));
int index = 10;
while (lineNumber < index - 1)
{
lineNumber++;
br.readLine();
}
String lineYouWant = br.readLine();
if (lineYouWant.isEmpty()) br.close();
// Do stuff with lineYouWant
br.close();

Since all of your lines are the same size you could look at the skip() method in the BufferedReader. You would basically read a line and then skip 10 * lineSize and read the next line, etc...

The purpose of a buffered reader is to make reading logical units like lines easy. Reading multiple lines would complicate your code and not provide a great performance boost since the buffered reader is already reading large blocks of data into its buffer.
Edit: Since your records are fixed size you could use a lower level reader and just read the amount of bytes required.

Java: Copy strings from a file to another without losing the 'newline format'

Sorry in advance if the title is misleading/wrong but this is the best I can do after a really long day spent practicing with Java. (my brain is melting)
I put this code togheter to read a file and copy it into another file, skipping the line/lines that begins with a given string (BeginOfTheLineToRemove). It actually works and remove the desired line, but, for some reason, it forgets about the \n (newline). Spacing and symbols are copied. I can't figure it out. I really hope someone will help. cheers from a java newb from italy ;)
public void Remover(String file, String BeginOfTheLineToRemove) {
File StartingFile = new File(file);
File EndingFile = new File(StartingFile.getAbsolutePath() + ".tmp");
BufferedReader br = new BufferedReader(new FileReader(file));
PrintWriter pw = new PrintWriter(new FileWriter(EndingFile));
String line;
while ((line = br.readLine()) != null) {
if (line.startsWith(LineToRemoveThatBeginWithThis)) {
continue;
}
pw.write(line);
}
pw.close();
br.close();
}

Use pw.println instead of pw.write. println adds new line character after it writes content.

You are using PrintWriter.write() to write the lines - This does not by default write newline at the end. Use println() instead.

This will probably help you.
The BufferedReader.readLine() method does not read any line termination characters. So therefore your line will not contain any termination characters.

BufferedReader#readLine documentation says:
Returns: A String containing the contents of the line, not including any line-termination characters, or null if the end of the stream has been reached
That is, the reader strips the line termination characters from your Strings, so you need to manually add them again:
// \n on Linux/Mac, \r\n on Windows
String lineSep = System.getProperty("line.separator");
pw.write(line);
pw.write(lineSep);

BufferedReader.readLine() uses the newline to identify the end of the line, and the string that it returns does not contain this newline. The newline is a separator, so it is not considered part of the data.
To compensate for this, you can add a newline to your output, like so:
while((line = br.readLine()) != null) {
if(line.startsWith(LineToRemoveThatBeginWithThis)) continue;
pw.write(line);
pw.println();
}
The extra call to PrintWriter.println() will print a newline after you write out your line of text.

Outside the loop get the system's line seperator:
String lineSeparator = System.getProperty("line.separator");
Then append that to the line you've read in:
pw.write(line+lineSeparator);

Counting Words and Newlines In A File Using Java?

I am writing a small java app which will scan a text file for any instances of particular word and need to have a feature whereby it can report that an instance of the word was found to be the 14th word in the file, on the third line, for example.
For this i tried to use the following code which i thought would check to see whether or not the input was a newline (\n) character and then incerement a line variable that i created:
FileInputStream fileStream = new FileInputStream("src/file.txt");
DataInputStream dataStream = new DataInputStream(fileStream);
BufferedReader buffRead = new BufferedReader(new InputStreamReader(dataStream));
String strLine;
String Sysnewline = System.getProperty("line.separator");
CharSequence newLines = Sysnewline;
int lines = 1;
while ((strLine = buffRead.readLine()) != null)
{
if(strLine.contains(newLines))
{
System.out.println("Line Found");
lines++;
}
}
System.out.println("Total Number Of Lines In File: " + lines);
This does not work for, it simply display 0 at the end of this file. I know the data is being placed into strLine during the while loop as if i change the code slightly to output the line, it is successfully getting each line from the file.
Would anyone happen to know the reason why the above code does not work?

Read the javadocs for readLine.
Returns:
A String containing the contents of the line, not including any line-termination characters, or null if the end of the stream has been reached

readLine() strips newlines. Just increment every iteration of the loop. Also, you're overcomplicating your file reading code. Just do new BufferedReader(new FileReader("src/file.txt"))