JDK-8196298: Add null Reader and Writer

[Patrick Reinhart]

> Am 01.02.2018 um 22:26 schrieb Brian Burkhalter <brian.burkhalter at oracle.com>:
> 
> 
> On Jan 30, 2018, at 8:52 AM, Patrick Reinhart <patrick at reini.net <mailto:patrick at reini.net>> wrote:
> 
>>> Am 30.01.2018 um 16:02 schrieb Alan Bateman <Alan.Bateman at oracle.com <mailto:Alan.Bateman at oracle.com>>:
>>> 
>>> […]
>>> 
>>> One other micro detail is that Reader/Writer support implementations specifying the object to use for synchronization. This isn't interesting for the Reader/Writer objects returned by the proposed static methods so a one-line that says that the object used to synchronize operations is not specified might help. It would avoid something synchronizing on the reader or writer and expecting operations read/write methods to block
>> 
>> Is that a difference from the null InputStream/OutputStream here?
> 
> Yes: there is no such lock instance variable for those classes. Probably it would not hurt to add a one liner to each method’s doc as Alan suggested.
> 

As my english is not that good, I could need some help for that one liner :-)

-Patrick