Configuration via Configuration object instead of overloaded methods

[pivovarit]

We're reaching a point where there's a significant number of things that can be configured:

• custom Executor
• maximum parallelism
• task batching
• thread factory used by a default Executor
• thread factory used by the internal Executor

My initial idea is to create a new set of methods that look more/less like this:

parallel(Function<T, R> mapper, Collector<R, ?, RR> collector, Configuration configuration) {
}

And now, instead of coming up and maintaining multiple versions of each method, everything could be passed via the Configuration object, for example:

var e = Executors.newFixedThreadPool(4);

Stream.of(1).collect(parallel(i -> i, toList(), on(e).withMaxParallelism(4)));

Naturally, all the existing methods would stay there for backward compatibility, but would be internally rewritten to leverage the configuration object