Request/discussion: BufferedReader reading using async API while providing sync API

Brunoais brunoaiss at
Fri Oct 21 17:56:43 UTC 2016

Pavel is right.

In reality, I was expecting such BufferedReader to use only a single 
buffer and have that Buffer being filled asynchronously, not in a 
different Thread.
Additionally, I don't have the intention of having a larger buffer than 
before unless stated through the API (the constructor).

In my idea, internally, it is supposed to use 
java.nio.channels.AsynchronousFileChannel or equivalent.

It does not prevent having two buffers and I do not intent to change 
BufferedReader itself. I'd do an BufferedAsyncReader of sorts (any name 
suggestion is welcome as I'm an awful namer).

On 21/10/2016 18:38, Roger Riggs wrote:
> Hi Pavel,
> I think Brunoais asking for a double buffering scheme in which the 
> implementation of
> BufferReader fills (a second buffer) in parallel with the application 
> reading from the 1st buffer
> and managing the swaps and async reads transparently.
> It would not change the API but would change the interactions between 
> the buffered reader
> and the underlying stream.  It would also increase memory requirements 
> and processing
> by introducing or using a separate thread and the necessary 
> synchronization.
> Though I think the formal interface semantics could be maintained, I 
> have doubts
> about compatibility and its unintended consequences on existing 
> subclasses,
> applications and libraries.
> $.02, Roger
> On 10/21/16 1:22 PM, Pavel Rappo wrote:
>> Off the top of my head, I would say it's not possible to change the 
>> design of an
>> _extensible_ type that has been out there for 20 or so years. All 
>> these I/O
>> streams from were designed for simple synchronous use case.
>> It's not that their design is flawed in some way, it's that they 
>> doesn't seem to
>> suit your needs. Have you considered using 
>> java.nio.channels.AsynchronousFileChannel
>> in your applications?
>> -Pavel
>>> On 21 Oct 2016, at 17:08, Brunoais <brunoaiss at> wrote:
>>> Any feedback on this? I'm really interested in implementing such 
>>> BufferedReader/BufferedStreamReader to allow speeding up my 
>>> applications without having to think in an asynchronous way or 
>>> multi-threading while programming with it.
>>> That's why I'm asking this here.
>>> On 13/10/2016 14:45, Brunoais wrote:
>>>> Hi,
>>>> I looked at BufferedReader source code for java 9 long with the 
>>>> source code of the channels/streams used. I noticed that, like in 
>>>> java 7, BufferedReader does not use an Async API to load data from 
>>>> files, instead, the data loading is all done synchronously even 
>>>> when the OS allows requesting a file to be read and getting a 
>>>> warning later when the file is effectively read.
>>>> Why Is BufferedReader not async while providing a sync API?

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