How to create a scala.collection.immutable.Seq from a Java List in Java?

Question

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;
    }
}

Solution 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.

Solution 2

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

Solution 3

You can use:

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

Solution 4

You can try this:

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

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