The flush method of OutputStream does nothing.
I just don't get this, maybe I'm just plain dumb,
but could someone explain me this.
If I have a DataOuputStream, and I call its
flush() method, what really happens?
The API doc of DataOutputStream says
Flushes this data output stream. This forces
any buffered output bytes to be written out to the stream.
The flush method of DataOuputStream calls the
flush method of its underlying output stream.
And the API doc of OutputStream says
The flush method of OutputStream does nothing.
What does this mean? Nothing happens? The
DataOutputStream just calls OutputStreams
flush(), which does nothing?
Or does it mean that the DataOutputStream.flush()
first forces the bytes to be written to stream and then
calls the OutputStreams flush(), which actually does nothing?
kari-matti
By default an OutputStream doesn't do any buffering, thus it's flush method doesn't need to do anything. If you've got a BufferedOutputStream, for example, then indeed some buffering will be done, thus calling flush() will have an effect.
Basically what I want to say is: The statement "The flush method of OutputStream does nothing" just tells you the behaviour of the default implementation, but classes extending OutputStream are free to change that behaviour, as long as it matches the contract defined in the API doc (and should do so, if its usefull).
Message was edited by:
JoachimSauer
> The flush method of DataOuputStream calls the
> flush method of its underlying output stream.
>
> And the API doc of OutputStream says
...
> What does this mean? Nothing happens?
>
> The DataOutputStream just calls OutputStreams
> flush(), which does nothing?
Do you know what an "abstract class" is? :) Who said that the "underlying stream" is a pure abstract OutputStream?
Hello Kari.,
This is Samba;
Nice to talk to you again.
And coming to the question... I didn't understand what you trying to know.
One thing is clear.
What BufferedOutputStream does when flush() method is callled is it forcefully pushes out any of the data that is in it's buffer to the output device(eg. file, console, frame,webpage,etc), even before the buffer is filled, which otherwise waits till the buffer is filled.
But DataOutputStream doesn't do any buffering , so there is no questioning of flushing out the data. May be To keep all the Stream Classes Consistentthe SUN has created a dummy method in DataOutputStream.
Tell me if you know any thing more,
Samba.
Message was edited by:
MasterJ
Thanks to all for their replys, I believe I'm less
dumb now :)
So, basically the class that extends the OutputStream
class has to implement the abstract methods of OutputStream
and do its own flushing if necessary, right?
So incase of DataOutputStream, and other classes that
doesn't have buffering, the flush() method only calls the
super class' flush() method?
And to Samba: Nice to hear from you, I wish all good for you.
kari-matti
