Efficient way to write InputStream to a File in Java 6

Question

I will get input stream from third party library to my application. I have to write this input stream to a file.

Following is the code snippet I tried:

private void writeDataToFile(Stub stub) { 
    OutputStream os = null;
    InputStream inputStream = null;

    try {

        inputStream = stub.getStream();
        os = new FileOutputStream("test.txt");
        int read = 0;
        byte[] bytes = new byte[1024];

        while ((read = inputStream.read(bytes)) != -1) {
            os.write(bytes, 0, read);
        }

    } catch (Exception e) {

        log("Error while fetching data", e);

    } finally {
        if(inputStream != null) {
            try {
                inputStream.close();
            } catch (IOException e) {
                log("Error while closing input stream", e);
            }
        }
        if(os != null) {
            try {
                os.close();
            } catch (IOException e) {
                log("Error while closing output stream", e);
            }
        }
    }
 }

Is there any better approach to do this ?

score 27 · Accepted Answer · edited Aug 16 '17 at 10:37

27

Since you are stuck with Java 6, do yourself a favour and use Guava and its Closer:

final Closer closer = Closer.create();
final InputStream in;
final OutputStream out;
final byte[] buf = new byte[32768]; // 32k
int bytesRead;

try {
    in = closer.register(createInputStreamHere());
    out = closer.register(new FileOutputStream(...));
    while ((bytesRead = in.read(buf)) != -1)
        out.write(buf, 0, bytesRead);
    out.flush();
} finally {
    closer.close();
}

Had you used Java 7, the solution would have been as simple as:

final Path destination = Paths.get("pathToYourFile");
try (
    final InputStream in = createInputStreamHere();
) {
    Files.copy(in, destination);
}

And yourInputStream would have been automatically closed for you as a "bonus"; Files would have handled destination all by itself.

edited Aug 16 '17 at 10:37

Bass

4,977
2
36
82

answered Mar 26 '14 at 14:23

fge

119,121
33
254
329

Files and Paths is the concept from Java 7. But my application is running with Java 6. Is there any solution like above is available in Java 6. – Awesome Mar 26 '14 at 14:33
Aw shucks. OK, then can you use an external library? I was thinking about Guava here – fge Mar 26 '14 at 14:34
FYI, the `Files` library is not available in **Android**'s Java 1.7. Got stung by this. http://stackoverflow.com/questions/24869323/android-import-java-nio-file-files-cannot-be-resolved – Joshua Pinter Jan 24 '15 at 22:24
the java 7 answer is not correct, with version 18 of guava at least – NimChimpsky Feb 11 '15 at 15:27
1

@JoshPinter yeah, you have to wonder why. This API is so much better than `File` that there's just no comparison. – fge Feb 11 '15 at 15:28
@fge my mistake I though you were using the guava Files api, which doesn't have a method matching the inputs – NimChimpsky Feb 11 '15 at 20:22

score 2 · Answer 2 · answered Mar 26 '14 at 14:36

If you're not on Java 7 and can't use fge's solution, you may want to wrap your OutputStream in a BufferedOutputStream

BufferedOutputStream os = new BufferedOutputStream(new FileOutputStream("xx.txt"));

Such buffered output stream will write bytes in blocks to the file, which is more efficient than writing byte per byte.

score 1 · Answer 3 · answered Mar 26 '14 at 14:27

1

It can get cleaner with an OutputStreamWriter:

OutputStream outputStream = new FileOutputStream("output.txt");
Writer writer = new OutputStreamWriter(outputStream);

writer.write("data");

writer.close();

Instead of writing a string, you can use a Scanner on your inputStream

Scanner sc = new Scanner(inputStream);
while (sc.HasNext())
    //read using scanner methods

answered Mar 26 '14 at 14:27

Brad Gardner

1,627
14
14

1

While a `.txt` file was mentioned by the OP, this solution has two major inconvenients: 1. `Scanner` will scrap the delimiter; 2. no encoding specified in the `Writer`. So, you will drop newlines (since this is the default delimiter of `Scanner`) _and_ you risk not using the correct encoding since what you receive are bytes, not chars. More details on this latter problem [here](http://fgaliegue.blogspot.com/2014/03/strings-characters-bytes-and-character.html). – fge Mar 26 '14 at 14:30

Efficient way to write InputStream to a File in Java 6

3 Answers3

Linked