How to create a scala.collection.immutable.Seq fro

问题:

I'm trying to get Akka going in my Java project, and I'm hung up on a small issue with the Seq type(s) from Scala. I'm able to convert my Java List of ActorRef into a scala.collection.Seq, but the Akka API I'm trying to use requires a scala.collection.immutable.Seq. How can I make one?

Code:

static class Router extends UntypedLoadBalancer {
    private final InfiniteIterator<ActorRef> workers;

    public Router(List<ActorRef> workers) {
        Seq workerSeq = asScalaBuffer(workers);

        // how to get from the scala.collection.Seq above to the instance of
        // scala.collection.immutable.Seq required by CyclicIterator below?
        this.workers = new CyclicIterator<ActorRef>();
    }

    public InfiniteIterator<ActorRef> seq() {
        return workers;
    }
}

回答1:

You can use scala.collection.JavaConversions.asScalaBuffer to convert the Java List to a Scala Buffer, which has a toList method, and a Scala List is a collection.immutable.Seq.

回答2:

The akka Java documentation for routers as well as the ScalaDoc for CyclicIterator both suggest that the CyclicIterator constructor takes a List.

回答3:

You can use:

scala.collection.JavaConverters.collectionAsScalaIterableConverter(workers).asScala().toSeq()

回答4:

You can try this:

scala.collection.JavaConverters.asScalaIteratorConverter(list.iterator()).asScala().toSeq();