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BufferedWriter is not writing to ByteArrayOutputStream

I want to convert an input stream to byte array. I know I can use IOUtils from commons-io. But I am practicing some basics in java io. I read an xml file using BufferedReader and tried writing it to a ByteArrayOutputStream using BufferedWriter. But its not working.
When I write directly to the ByteArrayOutputStream its working. Whats wrong in my code?
try (InputStream inputStream = getClass().getResourceAsStream(
"/productInventory.xml");
ByteArrayOutputStream arrayOutputStream = new ByteArrayOutputStream();
BufferedWriter bufferedWriter = new BufferedWriter(
new OutputStreamWriter(arrayOutputStream));
BufferedReader bufferedReader = new BufferedReader(
new InputStreamReader(inputStream));) {
String line = "";
while ((line = bufferedReader.readLine()) != null) {
bufferedWriter.write(line);
}
System.out.println(arrayOutputStream.size());
} catch (IOException e) {
e.printStackTrace();
}
When I include below line in the loop its working
arrayOutputStream.write(line.getBytes(), 0, line.getBytes().length);
What is wrong while using BufferedWriter?

Nothing's wrong - it's just buffering! :D
The BufferedWriter works by filtering everything you send into it into a buffer - when the buffer is full, or when the writer is closed, or flushed, (It's a Closeable, so you should absolutely close it), it sends along those buffered characters to the underlying writer.
If you want to see the underlying writer update you have to either:
1) Fill up the buffer (default size is 8k in Java)
2) Call .flush()
3) Call .close()
4) As mentioned in comments, you can do a try-with-resources to make the close implicit:
try (BufferedWriter writer = new BufferedWriter(underlyingWriter)) {
// doStuff
}

Download file line by line java

I know this question might sound really basic for most of you. I need to download a large file from server. The first line of this file contains a time tag. I want to download entire file only if my time tag mismatches to that of file. For this I'm using the given code. However, I'm not sure if this actually prevents file from uselessly downloading entire file.
Please help me out !
public String downloadString(String url,String myTime)
{
try {
URL url1 = new URL(url);
URLConnection tc = url1.openConnection();
tc.setConnectTimeout(timeout);
tc.setReadTimeout(timeout);
BufferedReader br = new BufferedReader(new InputStreamReader(tc.getInputStream()));
StringBuilder sb = new StringBuilder();
String line;
while ((line = br.readLine()) != null) {
if(line.contains(myTime))
{
Log.d("TIME CHECK", "Article already updated");
break;
}
sb.append(line+"\n");
}
br.close();
return sb.toString();
}
catch(Exception e)
{
Log.d("Error","In JSON downloading");
}
return null;
}

No, there is no easy way to control exactly to the last byte what will be downloaded. Even at the Java level you are involving a BufferedReader, which will obviously download more than you ask for, buffering it. There are other buffers as well, including at the OS level, which you cannot control. The proper technique to download only new files with HTTP is to use the IfModifiedSince header.

Your code won't download the whole file but as the BufferedReader has a default buffer size of 8192 you will read at least that many characters.

You can go byte-by-byte or chunk-by-chunk if it is the size
BufferedInputStream in = new BufferedInputStream(url).openStream())
byte data[] = new byte[1024];
int count;
while((count = in.read(data,0,1024)) != -1)
{
out.write(data, 0, count);
}
Check this question please
How to download and save a file from Internet using Java?

Convert InputStreamReader to InputStream

How can I convert InputStreamReader to InputStream? I have an InputStream which contains some string and byte data and I want to parse it. So I wrap my InputStream to BufferedReader. Then I read 3 lines from it. After that I want to get the rest of data(bytes) as is. But if I try to get it nothing happens.
Code snippet:
BufferedReader br = new BufferedReader(new InputStreamReader(is,"UTF-8"));
String endOfData = br.readLine();
String contentDisposition = br.readLine();
String contentType = br.readLine();
file = new File(filename);
if(file.exists()) file.delete();
file.createNewFile();
FileOutputStream fos = new FileOutputStream(file);
byte[] data = new byte[8192];
int len = 0;
while (-1 != (len = is.read(data)) )
{
fos.write(data, 0, len);
Log.e("len", len+"");
}
fos.flush();
fos.close();
is.close();
The file is empty. If I don't wrap InputStream it works fine, but I need to read 3 lines and remove it.
Thanks.

If you want to mix text and byte data together, you should use OutputStream.writeUTF to write out those 3 lines, this way one single InputStream will be able to retrieve all the data that you need.

Take a look at commons-io's ReaderInputStream: it is a little heavy handed, but you can wrap the BufferedReader with that and read it as an input stream again.

It's pretty hard to mix byte and character input correctly, especially once you start throwing buffered readers / streams into the mix. I'd suggest that you either pick one and stick with it (converting your bytes to strings as necessary; care with the encoding!) or wrap the entire thing in a ZipOutputStream so you can have multiple logical "files" with different contents.

java file reading issue

In my java application, I have to read one file. The problem what I am facing, after reading the file, the results is coming as non readable format. that means some ascii characters are displayed. That means none of the letters are readable. How can I make it display that?
// Open the file that is the first
// command line parameter
FileInputStream fstream = new FileInputStream("c:\\hello.txt");
// Get the object of DataInputStream
DataInputStream in = new DataInputStream(fstream);
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String strLine;
// Read File Line By Line
while ((strLine = br.readLine()) != null) {
// Print the content on the console
System.out.println(strLine);
}
// Close the input stream
in.close();
} catch (Exception e) {// Catch exception if any
System.err.println("Error: " + e.getMessage());
}

Perhaps you have an encoding error. The constructor you are using for an InputStreamReader uses the default character encoding; if your file contains UTF-8 text outside the ASCII range, you will get garbage. Also, you don't need a DataInputStream, since you aren't reading any data objects from the stream. Try this code:
FileInputStream fstream = null;
try {
fstream = new FileInputStream("c:\\hello.txt");
// Decode data using UTF-8
BufferedReader br = new BufferedReader(new InputStreamReader(in, "UTF-8"));
String strLine;
// Read File Line By Line
while ((strLine = br.readLine()) != null) {
// Print the content on the console
System.out.println(strLine);
}
} catch (Exception e) {// Catch exception if any
System.err.println("Error: " + e.getMessage());
} finally {
if (fstream != null) {
try { fstream.close(); }
catch (IOException e) {
// log failure to close file
}
}
}

The output you are getting is an ascii value ,so you need to type cast it into char or string before printing it.Hope this helps

You have to implement this way to handle:-
BufferedReader br = new BufferedReader(new InputStreamReader(in, encodingformat));
.
encodingformat - change it according to which type of encoding issue you are encounter.
Examples: UTF-8, UTF-16, ... soon
Refer this Supported Encodings by Java SE 6 for more info.

My problem got solved. I dont know how. I copied the hello.txt contents to another file and run the java program. I could read all letters. dont know whats the problem in that.

Since you doesn't know the encoding the file is in, use jchardet to detect the encoding used by the file and then use that encoding to read the file as others have already suggested. This is not 100 % fool proof but works for your scenario.
Also, use of DataInputStream is unnecessary.

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();
}
}
}