DataOutputStream() VS DataOutputStream(new BufferedOutputStream())

Question

The code at Java Tutorials showed an example of using DataOutputStream class and DataInputStream class.

A snippet of the code looks like this:

//..
out = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(dataFile)));
//..
in = new DataInputStream(new BufferedInputStream(new FileInputStream(dataFile)));
//..

I was wondering why is it required to create a new BufferedOutputStream when we create a new DataOutputStream ?

Isn't it redundant since this alternative works as well? : new DataOutputStream(new FileOutputStream(dataFile));

As this page claims, DataStreams already provides a buffered file output byte stream. So is "double-buffering" really required?

I've modified the 2 lines of code (output and input), taking away the BufferedOutputStream and BufferedInputStream and everything seems to work just fine, so I was wondering what is the purpose of the BufferedOutputStream and BufferedInputStream ?

Answer 1

Wrapping the FileOutputStream in a BufferedOutputStream will generally speed up the overall output of your program. This will only be noticeable if you are writing large amounts of data. The same thing goes for wrapping an InputStream in a BufferedInputStream. The use of buffers will only affect efficiency, not correctness.