Writing byte array to an UTF8-encoded file

Question

Given a byte array in UTF-8 encoding (as result of base64 decoding of a String) - what is please a correct way to write it to a file in UTF-8 encoding?

Is the following source code (writing the array byte by byte) correct?

OutputStreamWriter osw = new OutputStreamWriter(
 new FileOutputStream(tmpFile), Charset.forName("UTF-8"));
for (byte b: buffer)
 osw.write(b);
osw.close();

• Estimate: It's duplicated (stackoverflow.com/questions/1001540/…)
• Robert: If you already have a buffer of bytes you don't need a writer. A writer is for writing characters or Strings.
• RealSkeptic: Based on your comment on the answer below, are you sure your array is in UTF-8 encoding? It will only be so if the original data that was encoded in base64 was in UTF-8 itself. What was the input of your base64 encode?
• Alexander Farber: Some objects encoded with Base64.encode... (I know it's a stupid answer, but the source code is huge with 2500 Java files)
• RealSkeptic: That is the code of Base64, but what was encoded with it? Are you sure they were strings? Were they Java strings? Were they byte arrays that were converted from strings? If you don't know what the actual objects were, it's going to be hard to print them as you don't even know they are strings. You can encode anything in base64, including images and sounds.

Answer 1

Don't use a Writer. Just use the OutputStream. A complete solution using try-with-resource looks as follows:

try (FileOutputStream fos = new FileOutputStream(tmpFile)) {
 fos.write(buffer);
}

Or even better, as Jon points out below:

Files.write(Paths.get(tmpFile), buffer);

• Jon Skeet: Or Files.write to make it even simpler.
• Alexander Farber: When I use just OutputStream I get the error (later, when trying to use Efficient XML): Invalid byte 1 of 1-byte UTF-8 sequence. So I am trying to find a proper way to write the byte array to file in UTF-8 encoding
• aioobe: But you said the array is in UTF-8 encoding, no? I think you should check your assumptions. Make sure the buffer is indeed proper UTF-8 and that it represents something Efficient XML can handle.
• Nitin Dandriyal: I think the problem is while reading in that case, create a buffer read and write simultaneously