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.

Solution 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
}

Solution 2

Without any libraries:

try (FileOutputStream stream = new FileOutputStream(path)) {
    stream.write(bytes);
}

With Google Guava:

Files.write(bytes, new File(path));

With Apache Commons:

FileUtils.writeByteArrayToFile(new File(path), bytes);

All of these strategies require that you catch an IOException at some point too.

Solution 3

Another solution using java.nio.file:

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

Solution 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.

Solution 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();
}

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