>> The comment is misleading because in fact no byte is written at raw
>> level. That's because the data size is smaller than the buffer size and
>> the buffer is empty (was emptied by the last write call).

> It depends on the implementation. A different implementation may use a
> different algorithm.

I feel that no matter what implementation algorithm BufferedWriter uses
it shouldn't write smaller chunks of data than buffer's size or else the
buffer is useless.

>> I also think this is the
>> correct behavior regardless of implementation language of BufferedWriter
>> class i.e. no write call should write at raw level smaller chunks of
>> data than buffer's size unless it has to.

> But how do you decide when it "has to"? Unless you want to constrain the
> exact implemented algorithm, you can't do that in your tests.

When a direct or indirect (e.g. on close) flush is called for the file
object.