Hi All! So `SequenceInputStream()` takes a Java `Enumeration` as an argument, but at the moment I on...

# getting-started

[Alec Muffett]

Hi All! So SequenceInputStream() takes a Java Enumeration as an argument, but at the moment I only have a `List<InputStream>`; there's a workaround for this described at https://www.pushing-pixels.org/2018/08/15/converting-list-to-enumeration-in-kotlin.html to provide a List<T>.toEnumeration() method, but I am wondering if there's something more elegant?

[Vampire]

More elegant, but less performant as it will create n-1 Vector instances:

inList.reduce { left, right -> SequenceInputStream(left, right) }

Another way would be

SequenceInputStream(Vector(inList).elements())

[Alec Muffett]

Thanks, @Vampire

[Alec Muffett]

Looks like this might be an RFE?

[Vampire]

An asEnumeration() method?
Maybe

[nanodeath]

I made this:

private operator fun InputStream.plus(inputStream: InputStream): InputStream = SequenceInputStream(this, inputStream)

might be what you want

[Vampire]

Well, that's neat and probably enables inList.sum(), but it is basically the same as my reduce call and thus will create n-1 new Vector instances.

[nanodeath]

it doesn't create any Vector instances though

[Vampire]

Sure it does, look inside the SequenceInputStream constructor you are calling 😉

[nanodeath]

http://developer.classpath.org/doc/java/io/SequenceInputStream-source.html I don't see Vector anywhere

[nanodeath]

https://github.com/openjdk/jdk/blob/master/src/java.base/share/classes/java/io/SequenceInputStream.java er, this is probably the correct place to look these days

[nanodeath]

and it does indeed use a Vector

[Vampire]

The first link you gave was the implementation of GNU classpath which I was not even aware of. 😄

[Vampire]

I just navigated to the constructor from my IDE

[Vampire]

Of course this is an implementation detail and could be different in different implementations as you just have proved. 🙂

[nanodeath]

I feel like they only use Vector so they can keep using Enumeration internally 😕 rather than porting everything over to...idk, Iterable

[Vampire]

Yes, seems so.
SequenceInputStream is simply very old and pre-collections framework.
I wonder they didn't add a collections variant.

[nanodeath]

no doubt Guava has something similar/better

[Vampire]

Never used Guava.
Isn't it about collections, not about IO streams?

[nanodeath]

yes, but it also has kinda everything. I'm looking