JEP 102 Process Updates revised API draft

[Peter Levart]

On 02/13/2015 04:18 PM, David M. Lloyd wrote:
> On 02/13/2015 09:15 AM, Peter Levart wrote:
>> On 02/13/2015 03:22 PM, Paul Sandoz wrote:
>>>> >It*is*  inconvenient for the user to have to use wildcards in 
>>>> specifying types:
>>>> >
>>>> >CompletableFuture<? extends Process> cf = 
>>>> process.completableFuture();
>>>> >
>>>> >...but it doesn't hinder the use of above 'cf' quite so much as 
>>>> 'len' in List example above, since 'T' in CompletableFuture<T> is 
>>>> used mostly in co-variant positions. The only methods that use it 
>>>> in contra-variant positions are:
>>>> >
>>>> >cf.getNow(?);
>>>> >cf.complete(?);
>>>> >cf.obtrudeValue(?);
>>>> >
>>> What about the methods with a parameter type of:
>>>
>>>    CompletionStage<? extends T>
>>>
>>> such as applyToEither and acceptEither?
>>>
>>> Paul.
>>
>> Oh, I see.
>>
>> That's a problem, yes. And these two methods are actually very useful in
>> the context of processes - waiting for 1st of two processes to finish.
>>
>> So the signature can only be the following:
>>
>>      CompletableFuture<ProcessHandle> completableFuture();
>
> I hesitate to mention it, but as someone who has been frustrated by 
> this same problem on numerous occasions I feel I must suggest that 
> maybe... having a completableFuture method should just be dropped?  A 
> user should be able to implement it themselves fairly easily, right?  
> And they'd be able to sidestep problems like stack size and so on by 
> managing their own threads.
>

That's a good idea. If the following two methods were added to 
Process[Handle]:

     public class ProcessHandle {
         public ProcessHandle waitForUninterruptibly();
     }

     public class Process extends ProcessHandle {
         @Override
         public Process waitForUninterruptibly();
     }

One could get CompletableFuture(s) simply by:

         ProcessHandle ph = ...;

         CompletableFuture<ProcessHandle> phf = 
CompletableFuture.supplyAsync(ph::waitForUninterruptibly);

         Process p = ...;

         CompletableFuture<Process> pf = 
CompletableFuture.supplyAsync(p::waitForUninterruptibly);


Peter