How to convert OutputStream to String in Java (Android)?

Question

I am trying to read the string that I get inside an outputStream that in turn is written there by a ftp - from a ftp server.

I'm stuck at this problem for about 2 hours and I find it hard to belive that it's so difficult to solve.

Is there any nice solution for my problem?

Here's the relevant code:

boolean success = false;
 OutputStream outputStream = null;
 try {
 outputStream = new BufferedOutputStream(new FileOutputStream(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS) + "/" + fileName));
 success = ftp.retrieveFile("/ViatorAndroid/" + fileName, outputStream);
 } catch (Exception e) {
 Log.d("FTPDownloadLatestVersion", "e = " + e.getMessage() + " " + Arrays.toString(e.getStackTrace()));
 }
 outputStream.close();
 if (success) {
 
 String versionNumberString = outputStream.getString(); // ??? I need here a way to get the string inside this output stream. Any clue how???
 int versionNumber = Integer.parseInt(versionNumberString);
 Log.d("FTPGetLastestVersionCode", "VersionNumber = " + versionNumber);
 return BuildConfig.VERSION_CODE < versionNumber;
 }

• Joachim Sauer: Do you want the content in both the file and as a string?
• user15381310: No. I have the outputStream variable containing some kind of string. I need to have that content from that stream inside a string.
• Joachim Sauer: An output stream doesn't (normally) contain a string. It's a handle to "some place" that you can write stuff to. Unless that "some place" is explicitly a byte buffer or similar, it doesn't actually store what its written to. As an example: A FileOutputStream doesn't remember what you wrote to it. It simply writes it to a file and then forgets about it. You can construct a ByteArrayOutputStream where the "some place" is a byte array, but pretty much everything else is just a pointer to some other place.

Answer 1

If you just want the content in a string, you build a ByteArrayOutputStream that will collect all the bytes written to it, and then turn this into a String.

Something like

try (ByteArrayOutputStream baos=new ByteArrayOutputStream()){
 boolean success = ftp.retrieveFile("/ViatorAndroid/" + fileName, baos);
 if (success){
 String versionNumberString = new String(baos.toByteArray(),StandardCharsets.UTF_8);
 ...
 }
}