byte[] to file in Java

Question

With Java:

I have a byte[] that represents a file.

How do I write this to a file (ie. C:\myfile.pdf)

I know it's done with InputStream, but I can't seem to work it out.

Answer 1

Use Apache Commons IO

FileUtils.writeByteArrayToFile(new File("pathname"), myByteArray)

Or, if you insist on making work for yourself...

try (FileOutputStream fos = new FileOutputStream("pathname")) {
   fos.write(myByteArray);
   //fos.close(); There is no more need for this line since you had created the instance of "fos" inside the try. And this will automatically close the OutputStream
}

Answer 2

File f = new File(fileName);    
byte[] fileContent = msg.getByteSequenceContent();    

Path path = Paths.get(f.getAbsolutePath());
try {
    Files.write(path, fileContent);
} catch (IOException ex) {
    Logger.getLogger(Agent2.class.getName()).log(Level.SEVERE, null, ex);
}

Answer 3

Basic example:

String fileName = "file.test";

BufferedOutputStream bs = null;

try {

    FileOutputStream fs = new FileOutputStream(new File(fileName));
    bs = new BufferedOutputStream(fs);
    bs.write(byte_array);
    bs.close();
    bs = null;

} catch (Exception e) {
    e.printStackTrace()
}

if (bs != null) try { bs.close(); } catch (Exception e) {}

Answer 4

Also since Java 7, one line with java.nio.file.Files:

Files.write(new File(filePath).toPath(), data);

Where data is your byte[] and filePath is a String. You can also add multiple file open options with the StandardOpenOptions class. Add throws or surround with try/catch.

Answer 5

From Java 7 onward you can use the try-with-resources statement to avoid leaking resources and make your code easier to read. More on that here.

To write your byteArray to a file you would do:

try (FileOutputStream fos = new FileOutputStream("fullPathToFile")) {
    fos.write(byteArray);
} catch (IOException ioe) {
    ioe.printStackTrace();
}

Answer 6

Another solution using java.nio.file:

byte[] bytes = ...;
Path path = Paths.get("C:\\myfile.pdf");
Files.write(path, bytes);