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Getting different byte array than written to file when reading from file

I'm writing my byte array to a file:
PrintWriter pw = new PrintWriter(new FileOutputStream(fileOutput, true));
pw.write(new String(cryptogram, Charset.defaultCharset()));
pw.close();
Then, I am reading it from the file like this:
String cryptogramString = new String();
while (scPriv.hasNext()) {
linePriv = scPriv.nextLine();
cryptogramString += linePriv;
}
But I don't know how to make byte[] from cryptogramString. I'am trying this:
byte[] b = cryptogramString.getBytes(Charset.defaultCharset());
System.out.println(Arrays.toString(b));
System.out.println(Arrays.toString(cryptogram));
But it doesn't return the same values. Does anyone have an idea how to make this right?

You should decide whether you are writing text or binary.
Encrypted data is always binary which means you shouldn't be using Reader/Writer/String classes.
try (FileOutputstream out = new FileOutputStream(filename)) {
out.write(bytes);
}
to read back in
byte[] bytes = new byte[(int) (new File(filename).length())];
try (FileInputstream in = new FileInputStream(filename)) {
in.read(bytes);
}
I have a file that contains xml and then plain text, so i cant read a file as a whole
You also can't write binary into a text file. You can encode it using base64.
Storing base64 data in XML?

Reading from UTF-8 formatted pdf file and writing it to a writer in cp1252 format

I am trying to read from a pdf file using file streams and I want to write it to a writer in cp1252 encodeded format. Following is the code:
byte buf[] = new byte[8192];
InputStream is = new FileInputStream(f);
ByteArrayOutputStream oos = new ByteArrayOutputStream();
int c=0;
while ((c = is.read(buf)) != -1) {
oos.write(buf, 0, c);
}
byte out[] = oos.toByteArray();
String str = oos.toString(out,"UTF-8");
char[] ch = str.toCharArray();
writer.write(ch);
is.close();
oos.close();
But the output is erroneous as the text is not readable(not properly converted). How do I fix this ?

You are probably encountering an error while trying to read from the PDF file. Try using PDFBox for extracting text from the PDF file. It's probably one of the best ways to do so. Once you have the required text, you can then save it using cp1252 encoding.
You can check out examples of text extraction using PDFBox from here
Regarding conversion to cp1252, if you are using a Windows machine, then the default encoding is cp1252. So simply trying to save the text should hopefully save it in cp1252 encoding.

base 64 decode and write to doc file

I have a base64 encoded String . Which looks like this
UEsDBBQABgAIAAAAIQDhD46/jQEAACkGAAATAAgCW0NvbnRlbnRfVHlwZXNdLnhtbCCiBAIooAACAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA .
I decodeD the String and write it to word file using FileWriter. But When I tried opening the doc file i get an error saying corrupt data.
I would like to know what are the steps I need to follow to write the content to a word document after decoding the data . below is the code what I did and went wrong.
byte[] encodedBytes = stringBase64.getBytes();
byte[] decodedBytes = Base64.decodeBase64(encodedBytes);
String decodeString = new String(decodedBytes);
filewriter = new java.io.FileWriter("F:\xxx.docx”);
BufferedWriter bw = new BufferedWriter(fw);
bw.write(decodeString);

The decoded data isn't plain text data - it's just binary data. So write it with a FileStream, not a FileWriter:
// If your Base64 class doesn't have a decode method taking a string,
// find a better one!
byte[] decodedBytes = Base64.decodeBase64(stringBase64);
// Note the try-with-resources block here, to close the stream automatically
try (OutputStream stream = new FileOutputStream("F:\\xxx.doc")) {
stream.write(decodedBytes);
}
Or even better:
byte[] decodedBytes = Base64.decodeBase64(stringBase64);
Files.write(Paths.get("F:\\xxx.doc"), decodedBytes);

Please have a look.
byte[] encodedBytes = /* your encoded bytes*/
// Decode data on other side, by processing encoded data
byte[] decodedBytes= Base64.decodeBase64(encodedBytes );
String yourValue=new String(decodedBytes);
System.out.println("Decoded String is " + yourValue);
Now further you can write this string into a file and read further.

Trying to Change the Encdoing of a File in Java is Doubling the Contents of the File

I have a FileOutputStream in java that is reading the contents of UDP packets and saving them to a file. At the end of reading them, I sometimes want to convert the encoding of the file. The problem is that currently when doing this, it just ends up doubling all the contents of the file. The only workaround that I could think to do would be to create a temp file with the new encoding and then save it as the original file, but this seems too hacky.
I must be just overlooking something in my code:
if(mode.equals("netascii")){
byte[] convert = new byte[(int)file.length()];
FileInputStream input = new FileInputStream(file);
input.read(convert);
String temp = new String(convert);
convert = Charset.forName("US-ASCII").encode(temp).array();
fos.write(convert);
}
JOptionPane.showMessageDialog(frame, "Read Successful!");
fos.close();
}
Is there anything suspect?
Thanks in advance for any help!

The problem is the array of bytes you've read from the InputStream will be converted as if its ascii chars, which I'm assuming its not. Specify the InputStream encoding when converting its bytes to String and you'll get a standard Java string.
I've assumed UTF-16 as the InputStream's encoding here:
byte[] convert = new byte[(int)file.length()];
FileInputStream input = new FileInputStream(file);
// read file bytes until EOF
int r = input.read(convert);
while(r!=-1) r = input.read(convert,r,convert.length);
String temp = new String(convert, Charset.forName("UTF-16"));

Different sizes of file in storing String v/s ByteArray in File android

I am using this approach for storing data in a file from responce of Server.
ByteArrayOutputStream outstream = new ByteArrayOutputStream();
response.getEntity().writeTo(outstream);
byte[] responseBody = outstream.toByteArray();
String data = new String(responseBody);
FileOutputStream out = new FileOutputStream(new File(my_path));
out.write(data.getBytes());
out.flush();
out.close();
It's working fine and my file gets created and size of it is 3786 bytes.
Now consider this ,
ByteArrayOutputStream outstream = new ByteArrayOutputStream();
response.getEntity().writeTo(outstream);
byte[] responseBody = outstream.toByteArray();
FileOutputStream out = new FileOutputStream(new File(my_path));
out.write(responseBody);
out.flush();
out.close();
it gives filesize of 1993 bytes.
Can anybody help me understand this , Does this new String(responseBody) do something to responcebytes like some encoding ?
Any help would be appreciated.

Yes, constructing a String from bytes decodes the bytes according to the current default character encoding (if one is not explicitly specified). Also String.getBytes() does the same in reverse (and may not necessarily produce the same sequence of bytes that was used to create it).
A String holds text. If your data is raw binary data and is intended to be treated as such, you should not be storing it in a String, you should be storing it in a byte[].
There is no need to have String data at all in that first bit, just write the byte[] to the file:
byte[] responseBody = outstream.toByteArray();
String data = new String(responseBody);
...
out.write(data.getBytes());
Can just be:
byte[] responseBody = outstream.toByteArray();
...
out.write(responseBody);