JDK 16 RFR of JDK-8250244: Address reliance on default constructors in java.net

[Joe Darcy]

Hi Alan,

On 7/24/2020 3:34 AM, Alan Bateman wrote:
> On 24/07/2020 01:33, Joe Darcy wrote:
>> Hello,
>>
>> Please review the replacement of default constructors in various 
>> abstract classes in java.net with explicit constructors:
>>
>>     webrev: http://cr.openjdk.java.net/~darcy/8250244.0/
>>     CSR: https://bugs.openjdk.java.net/browse/JDK-8250245
>>
>> (This is part of a larger effort to remove default constructor usage 
>> from the JDK in preparation for enabling a new lint warning.)
> Could we use the opportunity to change some of these to be protected? 
> For some of these then I don't think there is any compatibility impact.
>
At least from a few minutes thinking, I don't see a meaningful 
compatibility issue in replacing

1) a public constructor in an abstract class

with

2) a protected constructor in an abstract class

It is source compatible, subclasses would have access to the constructor 
in either case, and should also be binary compatible as linkage 
shouldn't be impacted (because subclasses would still have access to the 
constructor).

That said, for this exercise I'd prefer to replace the implicit default 
constructors with equivalent explicit ones, but would be open to future 
refinements to make the constructors protected.

Thanks,

-Joe