RFR: 8319123: Implement JEP 461: Stream Gatherers (Preview) [v13]

[Svein Otto Solem]

I tried to understand the GathererOp class and came over a small detail concering Gatherer.Integrator.

The two gatheres below are equivalent, both are greedy.

Gatherer.Integrator.Greedy<Void, String, Integer> voidStringIntegerGreedy = (v, s, downStream) -> downStream.push(s.length());

     var greedy1 = Gatherer.of(Gatherer.Integrator.ofGreedy(voidStringIntegerGreedy));
     var greedy2 = Gatherer.of(Gatherer.Integrator.of(voidStringIntegerGreedy));

Inlining the lambda makes them different.

     var greedy = Gatherer.of(Gatherer.Integrator.ofGreedy((v, s, downStream) -> downStream.push(s.length())));
     var nonGreedy = Gatherer.of(Gatherer.Integrator.of((v, s, downStream) -> downStream.push(s.length())));

If this can be a problem an introduction of an Integrator subtype like NonGreedy would have given a compiler error on the "var greedy2 =" line instead.

interface Integrator {
      .....
     static <A, T, R> NonGreedy<A, T, R> of(NonGreedy<A, T, R> integrator) {
            return integrator;
        }

        static <A, T, R> Greedy<A, T, R> ofGreedy(Greedy<A, T, R> greedy) {
            return greedy;
        }

        interface Greedy<A, T, R> extends Integrator<A, T, R> { }
        interface NonGreedy<A, T, R> extends Integrator<A, T, R> { }
  
}

Svein Otto Solem
Retired programmer
Kantega





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