What is the advantage of forking a stream over just using multiple streams?
For me this doesn't make much sense with an array list as stream source.
If the stream source is a big file that you process with
StreamForker<Person> forker = new StreamForker<>( java.nio.file.Files.lines(Paths.get("somepath")) .map(Person::new)) .fork(...)then it could prove beneficial since you would process the whole file only once, whereas with three seperat calls to Files.lines(...) you would read the file three times.