Unable to iterate Java List in Scala

I'm using the Java Twitter4J library in a Scala project.

I'm calling the method

twitter.开发者_JS百科getFriendsStatuses()

This method returns a list of twitter4j.User objects containing statuses.

I try to iterate over them and it goes in an infinite loop over the first element:

val users:List[User] = twitter.getFriendsStatuses(userId, paging.getSinceId())
while( users.iterator.hasNext() ) {
  println(users.iterator.next().getStatus())
}

Any ideas?

I guess users.iterator produces the new iterator each time it's evaluated. Try this:

val it = users.iterator
while(it.hasNext() ) {
   println(it.next().getStatus())
}

If you use Scala 2.8, you could use JavaConversion to convert Java collection to Scala collection automatically.

Ex.

import scala.collection.JavaConversions._

// Java Collection
val arrayList = new java.util.ArrayList[Int]
arrayList.add(2)
arrayList.add(3)
arrayList.add(4)

// It will implicitly covert to Scala collection, 
// so you could use map/foreach...etc.
arrayList.map(_ * 2).foreach(println)

What's wrong with just

users.foreach(user => println(user.getStatus()))

or even

users.map(_.getStatus()).foreach(println _)

or, if you're worried about traversing the collection twice

users.view.map(_.getStatus()).foreach(println _)

IOW: Why do you want to manage the iteration yourself (and possibly make mistakes), when you can just let someone else do the work for you?

I prefer scalaj-collection to scala.collection.JavaConversions. This makes the conversions explicit:

import scalaj.collection.Implicits._

val arrayList = new java.util.ArrayList[Int]
arrayList.add(2)
arrayList.add(3)
arrayList.add(4)

arrayList.asScala.map(_ * 2).foreach(println)

Available here: https://github.com/scalaj/scalaj-collection

I suggest using

scala.collection.JavaConverters._

and simply add .asScala to every object you wish to iterate