Java-DataOutputStream writeLong \\ Byte \\ Double \\ Int Speed

Question

I implemented a way to write primitive Java types to a binary output file using DataOutputStream 's writeX methods, but I'm observing 60-fold slower performance relative to a previous implementation that writes to a text file via a BufferedWriter .

I create my output stream like so:

DataOutputStream outFile = new DataOutputStream(new FileOutputStream("fileLoc"));

I use this method to write to such streams:

public static void writeFunctionPoint (DataOutputStream outFile, FunctFileSortCriterion functPt) throws IOException
{
    outFile.writeLong   (functPt.time);
    outFile.writeBytes  (functPt.dfid);
    outFile.writeDouble (functPt.value);
    outFile.writeInt    (functPt.qualifier);

}   // end method writeFunctionPoint

Why is my new approach so much slower than my old one?

Answer 1

You started out using a BufferedWriter and switched to an unbuffered OutputStream . I/O buffering can have a tremendous impact on performance, especially if you're writing a large number of small pieces. Insert a BufferedOutputStream :

DataOutputStream outFile = new DataOutputStream(
        new BufferedOutputStream(
        new FileOutputStream("fileLoc")));

That ought to get you a substantial speedup vs. where you are now. You can also try tweaking the buffer size to tune the performance a bit. I can't say how that will compare to your original BufferedWriter -based implementation, however; I'd guess it will be at least comparable, but performance is very hard to predict in general. It is essential to test.