8228392: java.io.Filter{In,Out}put stream constructors should allow null stream parameter

[Brian Burkhalter]

> On Jul 20, 2019, at 12:44 AM, Alan Bateman <Alan.Bateman at oracle.com> wrote:
> 
> On 19/07/2019 15:58, Brian Burkhalter wrote:
>> 
>> Given the compatibility issues it might be best to modify the specifications of the Filter*Stream subclass constructors to allow a null underlying stream parameter, thereby overriding the package level javadoc. IOTW align the spec with longstanding behavior.
>> 
> I think it will need a detailed examination to see how each one behaves when the input stream is null. As the field is protected it means that sub-classes can change its value at any time, maybe because they want to set it lazily or maybe they want to set it to null when the stream is closed. For classes such as DIS/DOS then it probably means NPE in many operations when the stream is null. Other classes (suchas BIS and BOS) will interpret it as the closed stream. So it will need a detailed analysis but more than likely you will not be able to change long standing behavior because it will break existing code.

Agreed. For sure in at least two of the five subclasses in java.io <http://java.io/> (not counting the deprecated LineNumberInputStream) breakage was observed (BufferedInputStream and DataInputStream). I can take another look but I doubt it is modifiable aside from making the doc match the behavior.

Brian