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Copy content from one file to multiple file using java

FileInputStream Fread = new FileInputStream("somefilename");
FileOutputStream Fwrite = null;
for (int i = 1; i <= 5; i++)
{
String fileName = "file" + i + ".txt";
Fwrite = new FileOutputStream(fileName);
int c;
while ((c = Fread.read()) != -1)
{
Fwrite.write((char) c);
}
Fwrite.close();
}
Fread.close();
The above code writes only to one file. How to make it work to write the content of one file to multiple files?

FYI: Note that the read() method you used returns a byte, not a char, so calling write((char) c) should have been just write(c).
To write to multiple files in parallel when copying a file, you create a array of output streams for the destination files, then iterate the array to write the data to all of them.
For better performance, you should always do this using a buffer. Writing one byte at a time will not perform well.
public static void copyToMultipleFiles(String inFile, String... outFiles) throws IOException {
OutputStream[] outStreams = new OutputStream[outFiles.length];
try {
for (int i = 0; i < outFiles.length; i++)
outStreams[i] = new FileOutputStream(outFiles[i]);
try (InputStream inStream = new FileInputStream(inFile)) {
byte[] buf = new byte[16384];
for (int len; (len = inStream.read(buf)) > 0; )
for (OutputStream outStream : outStreams)
outStream.write(buf, 0, len);
}
} finally {
for (OutputStream outStream : outStreams)
if (outStream != null)
outStream.close();
}
}

You will have to create multiple instances of FileOutputStream fwrite1, fwrite2, fwrite3, one per each file you want to write to, then, as you read, you simply write to all of them. This is how you achieve it.

Add this line:
Fread.reset();
after Fwrite.close();
And change the first line of code to this:
InputStream Fread = new BufferedInputStream(new FileInputStream("somefilename"));
Fread.mark(0);

The FReadstream gets to the end once and then there is nothing to make it start from the beginning.
To solve this you can:
call to FRead.reset() after each file writing
cache FRead's value somewhere and write to FWrite from this source
create an array / collection of FileOutputStream and write each byte to all of them during iteration
The recommended solution is of course the first one.
Also there are some problems in your code:
You are highly encouraged to use try-with-resouce for Streams as they should be safely closed
You seem to not follow naming conventions which say to name variables in lowerCamelCase

Java - open txt file and clear all multiple spaces

I have a txt file and what I am trying to do is open it and delete all multiple spaces so they become only one. I use:
br = new BufferedReader(new FileReader("C:\\Users\\Chris\\Desktop\\file_two.txt"));
bw = new BufferedWriter(new FileWriter("C:\\Users\\Chris\\Desktop\\file_two.txt"));
while ((current_line = br.readLine()) != null) {
//System.out.println("Here.");
current_line = current_line.replaceAll("\\s+", " ");
bw.write(current_line);
}
br.close();
bw.close();
However, as it seems correct according to me at least, nothing is written on the file. If I use a system.out.println command, it is not printed, meaning that execution is never in the while loop... What do I do wrong? Thanks

you are reading the file and at the same time writing contents on it..it is not allowed...
so better way to read the file first and store the processed text in another file and finally replace the original file with the new one..try this
br = new BufferedReader(new FileReader("C:\\Users\\Chris\\Desktop\\file_two.txt"));
bw = new BufferedWriter(new FileWriter("C:\\Users\\Chris\\Desktop\\file_two_copy.txt"));
String current_line;
while ((current_line = br.readLine()) != null) {
//System.out.println("Here.");
current_line = current_line.replaceAll("\\s+", " ");
bw.write(current_line);
bw.newLine();
}
br.close();
bw.close();
File copyFile = new File("C:\\Users\\Chris\\Desktop\\file_two_copy.txt");
File originalFile = new File("C:\\Users\\Chris\\Desktop\\file_two.txt");
originalFile.delete();
copyFile.renameTo(originalFile);
it may help...

There are few problems with your approach:
Main one is that you are trying to read and write to same file at the same time.
other is that new FileWriter(..) always creates new empty file which kind of prevents FileReader from reading anything from your file.
You should read content from file1 and write its modified version in file2. After that replace file1 with file2.
Your code can look more or less like
Path input = Paths.get("input.txt");
Path output = Paths.get("output.txt");
List<String> lines = Files.readAllLines(input);
lines.replaceAll(line -> line.replaceAll("\\s+", " "));
Files.write(output, lines);
Files.move(output, input, StandardCopyOption.REPLACE_EXISTING);

You must read first then write, you are not allowed to read and write to the same file at the same time, you would need to use RandomAccessFile to do that.
If you don't want to learn a new technique, you will need to either write to a separate file, or cache all lines to memory(IE an ArrayList) but you must close the BufferedReader before you Initialize your BufferedWriter, or it will get a file access error.
Edit:
In case you want to look into it, here is a RandomAccessFile use case example for your intended use. It is worth pointing out this will only work if the final line length is less than or equal to the original, because this technique is basically overwriting the existing text, but should be very fast with a small memory overhead and would work on extremely large files:
public static void readWrite(File file) throws IOException{
RandomAccessFile raf = new RandomAccessFile(file, "rw");
String newLine = System.getProperty("line.separator");
String line = null;
int write_pos = 0;
while((line = raf.readLine()) != null){
line = line.replaceAll("\\s+", " ") + newLine;
byte[] bytes = line.getBytes();
long read_pos = raf.getFilePointer();
raf.seek(write_pos);
raf.write(bytes, 0, bytes.length);
write_pos += bytes.length;
raf.seek(read_pos);
}
raf.setLength(write_pos);
raf.close();
}

How can I read a .txt file into a single Java string while maintaining line breaks?

Virtually every code example out there reads a TXT file line-by-line and stores it in a String array. I do not want line-by-line processing because I think it's an unnecessary waste of resources for my requirements: All I want to do is quickly and efficiently dump the .txt contents into a single String. The method below does the job, however with one drawback:
private static String readFileAsString(String filePath) throws java.io.IOException{
byte[] buffer = new byte[(int) new File(filePath).length()];
BufferedInputStream f = null;
try {
f = new BufferedInputStream(new FileInputStream(filePath));
f.read(buffer);
if (f != null) try { f.close(); } catch (IOException ignored) { }
} catch (IOException ignored) { System.out.println("File not found or invalid path.");}
return new String(buffer);
}
... the drawback is that the line breaks are converted into long spaces e.g. " ".
I want the line breaks to be converted from \n or \r to <br> (HTML tag) instead.
Thank you in advance.

What about using a Scanner and adding the linefeeds yourself:
sc = new java.util.Scanner ("sample.txt")
while (sc.hasNext ()) {
buf.append (sc.nextLine ());
buf.append ("<br />");
}
I don't see where you get your long spaces from.

You can read directly into the buffer and then create a String from the buffer:
File f = new File(filePath);
FileInputStream fin = new FileInputStream(f);
byte[] buffer = new byte[(int) f.length()];
new DataInputStream(fin).readFully(buffer);
fin.close();
String s = new String(buffer, "UTF-8");

You could add this code:
return new String(buffer).replaceAll("(\r\n|\r|\n|\n\r)", "<br>");
Is this what you are looking for?

The code will read the file contents as they appear in the file - including line breaks.
If you want to change the breaks into something else like displaying in html etc, you will either need to post process it or do it by reading the file line by line. Since you do not want the latter, you can replace your return by following which should do the conversion -
return (new String(buffer)).replaceAll("\r[\n]?", "<br>");

StringBuilder sb = new StringBuilder();
try {
InputStream is = getAssets().open("myfile.txt");
byte[] bytes = new byte[1024];
int numRead = 0;
try {
while((numRead = is.read(bytes)) != -1)
sb.append(new String(bytes, 0, numRead));
}
catch(IOException e) {
}
is.close();
}
catch(IOException e) {
}
your resulting String: String result = sb.toString();
then replace whatever you want in this result.

I agree with the general approach by #Sanket Patel, but using Commons I/O you would likely want File Utils.
So your code word look like:
String myString = FileUtils.readFileToString(new File(filePath));
There is also another version to specify an alternate character encoding.

You should try org.apache.commons.io.IOUtils.toString(InputStream is) to get file content as String. There you can pass InputStream object which you will get from
getAssets().open("xml2json.txt") *<<- belongs to Android, which returns InputStream*
in your Activity. To get String use this :
String xml = IOUtils.toString((getAssets().open("xml2json.txt")));
So,
String xml = IOUtils.toString(*pass_your_InputStream_object_here*);

my code hangs but when i debug it it never hangs

i have a java code that SOMETIMES hangs when i run it.Its a put command that puts through sockets( and input stream etc a file from a server to a client) . Sometimes this works but sometimes it doesnt and i get an error message. i tried every possible path that can be taken through debugging and i can never get it to hang. Is there a way to inspect the thing when its hang through eclipse?`
if (sentence.length() > 3 && sentence.substring(0, 3).equals("put")) {
File checkFile = new File(dir.getCurrentPath(), sentence.substring(4));
if (checkFile.isFile() && checkFile.exists()) {
try {
outToServer.writeBytes(sentence + "\n");
boolean cont = false;
String x;
while (!cont) {
if ((x = inFromServer.readLine()).equals("continue")) {
cont = true;
}
}
String name = sentence.substring(4);
copy.copyFile(name);
// outToServer.writeBytes("continue" + "\n");
this is the client code that recieves the PUT request(i.e. put test.txt takes the file test.txt and puts it in the server's local dir.
Copy file: (the thing that copies the data)
File checkFile = new File(dir.getCurrentPath(), file);
if (checkFile.isFile() && checkFile.exists()) {
DataOutputStream outToClient = new DataOutputStream(socket.getOutputStream());
// byte[] receivedData = new byte[8192];
File inputFile = new File(dir.getCurrentPath(), file);
byte[] receivedData = new byte[(int) inputFile.length()];
// String theLength = "" + inputFile.length();
outToClient.writeBytes("" + inputFile.length() + "\n");
BufferedInputStream bis = new BufferedInputStream(new FileInputStream(getCopyPath(file)));
// if (extension.equals("")) {
// extension = "txt";
// }
// BufferedReader inFromClient = new BufferedReader(new InputStreamReader(socket.getInputStream()));
// boolean cont = false;
// while (!cont) {
// if (inFromClient.readLine().equals("continue")) {
// cont = true;
//
// }
// }
// outToClient.writeBytes("continue" + "\n");
bis.read(receivedData, 0, receivedData.length);
OutputStream os = socket.getOutputStream();
os.write(receivedData, 0, receivedData.length);
// outToClient.writeBytes("finish" + "\n");
os.flush();
Protocol on server(copies stuff in the file)
if (get.equals("put")) {
//so the client sends: the put request
//then sends the length
try {
BufferedReader inFromClient = new BufferedReader(new InputStreamReader(socket.getInputStream()));
DataOutputStream outToClient = new DataOutputStream(socket.getOutputStream());
outToClient.writeBytes("continue" + "\n");
int length = Integer.parseInt(inFromClient.readLine());
// String x = "";
// boolean cont = false;
// while (!cont) {
// String temp = inFromClient.readLine();
// if (temp.equals("finish")) {
// cont = true;
// }
// else {
// x += temp;
// }
// }
byte[] recieveFile = new byte[length];
InputStream is = socket.getInputStream();
FileOutputStream fos = new FileOutputStream("Copy " + input.substring(4));
BufferedOutputStream bos = new BufferedOutputStream(fos);
int bytesRead;
int current = 0;
bytesRead = is.read(recieveFile, 0, recieveFile.length);
current = bytesRead;
If you cant answer the question in specific just tell me how i can debug the code that hangs or how i can debug concurrent code.(by the way the way that the signal passing is done is by passing a token as you can see i.e. the server sents a continue token that tells the client to start sending data, i havent done this with threads methods notify and wait since i cant use , since any single object has only 1 method.

when your process hangs, get the current stack dump for the process. this will show you why the process is hung.
note, you have at least one bug in your program, in that you are not handling the return value from the InputStream.read() method which will, at the very least, cause you to have busted data on the server side. (see #rk2010's answer for more details).
you main bug, though, is that when you wrap the BufferedReader around the socket InputStream, you are probably going to end up "stealing" more bytes from the stream than the just length value. when a BufferedReader reads data from the underlying stream, it can read more data than it actually returns in the readLine() method (so, it may read 1000 chars internally, but the first "line" may only contain 20 chars). if you continue to use the BufferedReader, everything is fine, but if you discard the BufferedReader and try to read more data from the underlying stream, you will have less data there than you expect. so, when you go to read the file contents, there aren't enough bytes available.
instead, you should be using DataOutputStream/DataInputStream exclusively. write the length as a long value (i.e. DataOutputStream.writeLong(long)), then write the bytes after (i.e. DataOutputStream.write(byte[])). then read the data using the corresponding methods in DataInputStream. since you can use the DataInputStream exclusively when reading (first to read the file size and then to read the actual file bytes), you don't risk losing bytes when switching read "modes" (additionally, DataInputStream does not do any internal buffering like BufferedReader). don't use Readers/Writers at all.

add logging after every read and write command. Give each thread a name.
run the program, see how the log matches up with what you expect.
note that you can't always rely on read method like the way you are. Safe way to read is by looping until you get a negative length.
int len = -1;
byte[] buff = new byte[1024]; // for 4KB, use: 4* 1024
while ( (len = is.read(buff, 0, buff.length)) > -1){
// copy len number of bytes from buff array into some other place.
}
Check out IOUtils.copy method
from Apache Commons IOUtils class

Prepend lines to file in Java

Is there a way to prepend a line to the File in Java, without creating a temporary file, and writing the needed content to it?

No, there is no way to do that SAFELY in Java. (Or AFAIK, any other programming language.)
No filesystem implementation in any mainstream operating system supports this kind of thing, and you won't find this feature supported in any mainstream programming languages.
Real world file systems are implemented on devices that store data as fixed sized "blocks". It is not possible to implement a file system model where you can insert bytes into the middle of a file without significantly slowing down file I/O, wasting disk space or both.
The solutions that involve an in-place rewrite of the file are inherently unsafe. If your application is killed or the power dies in the middle of the prepend / rewrite process, you are likely to lose data. I would NOT recommend using that approach in practice.
Use a temporary file and renaming. It is safer.

There is a way, it involves rewriting the whole file though (but no temporary file). As others mentioned, no file system supports prepending content to a file. Here is some sample code that uses a RandomAccessFile to write and read content while keeping some content buffered in memory:
public static void main(final String args[]) throws Exception {
File f = File.createTempFile(Main.class.getName(), "tmp");
f.deleteOnExit();
System.out.println(f.getPath());
// put some dummy content into our file
BufferedWriter w = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(f)));
for (int i = 0; i < 1000; i++) {
w.write(UUID.randomUUID().toString());
w.write('\n');
}
w.flush();
w.close();
// append "some uuids" to our file
int bufLength = 4096;
byte[] appendBuf = "some uuids\n".getBytes();
byte[] writeBuf = appendBuf;
byte[] readBuf = new byte[bufLength];
int writeBytes = writeBuf.length;
RandomAccessFile rw = new RandomAccessFile(f, "rw");
int read = 0;
int write = 0;
while (true) {
// seek to read position and read content into read buffer
rw.seek(read);
int bytesRead = rw.read(readBuf, 0, readBuf.length);
// seek to write position and write content from write buffer
rw.seek(write);
rw.write(writeBuf, 0, writeBytes);
// no bytes read - end of file reached
if (bytesRead < 0) {
// end of
break;
}
// update seek positions for write and read
read += bytesRead;
write += writeBytes;
writeBytes = bytesRead;
// reuse buffer, create new one to replace (short) append buf
byte[] nextWrite = writeBuf == appendBuf ? new byte[bufLength] : writeBuf;
writeBuf = readBuf;
readBuf = nextWrite;
};
rw.close();
// now show the content of our file
BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(f)));
String line;
while ((line = reader.readLine()) != null) {
System.out.println(line);
}
}

You could store the file content in a String and prepend the desired line by using a StringBuilder-Object. You just have to put the desired line first and then append the file-content-String.
No extra temporary file needed.

No. There are no "intra-file shift" operations, only read and write of discrete sizes.

It would be possible to do so by reading a chunk of the file of equal length to what you want to prepend, writing the new content in place of it, reading the later chunk and replacing it with what you read before, and so on, rippling down the to the end of the file.
However, don't do that, because if anything stops (out-of-memory, power outage, rogue thread calling System.exit) in the middle of that process, data will be lost. Use the temporary file instead.

private static void addPreAppnedText(File fileName) {
FileOutputStream fileOutputStream =null;
BufferedReader br = null;
FileReader fr = null;
String newFileName = fileName.getAbsolutePath() + "#";
try {
fileOutputStream = new FileOutputStream(newFileName);
fileOutputStream.write("preappendTextDataHere".getBytes());
fr = new FileReader(fileName);
br = new BufferedReader(fr);
String sCurrentLine;
while ((sCurrentLine = br.readLine()) != null) {
fileOutputStream.write(("\n"+sCurrentLine).getBytes());
}
fileOutputStream.flush();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
fileOutputStream.close();
if (br != null)
br.close();
if (fr != null)
fr.close();
new File(newFileName).renameTo(new File(newFileName.replace("#", "")));
} catch (IOException ex) {
ex.printStackTrace();
}
}
}