How can I convert a Java Iterable to a Scala Iterable? - scala

Question

Is there an easy way to convert a
java.lang.Iterable[_]
to a
Scala.Iterable[_]
?

Answer 1

In Scala 2.8 this became much much easier, and there are two ways to achieve it. One that's sort of explicit (although it uses implicits):
import scala.collection.JavaConverters._
val myJavaIterable = someExpr()
val myScalaIterable = myJavaIterable.asScala
EDIT: Since I wrote this, the Scala community has arrived at a broad consensus that JavaConverters is good, and JavaConversions is bad, because of the potential for spooky-action-at-a-distance. So don't use JavaConversions at all!
And one that's more like an implicit implicit: :)
import scala.collection.JavaConversions._
val myJavaIterable = someExpr()
for (magicValue <- myJavaIterable) yield doStuffWith(magicValue)

Answer 2

Yes use implicit conversions:
import java.lang.{Iterable => JavaItb}
import java.util.{Iterator => JavaItr}
implicit def jitb2sitb[T](jit: JavaItb[T]): Iterable[T] = new SJIterable(jit);
implicit def jitr2sitr[A](jit: JavaItr[A]): Iterator[A] = new SJIterator(jit)
Which can then be easily implemented:
class SJIterable[T](private val jitb: JavaItr[T]) extends Iterable[T] {
def elements(): Iterator[T] = jitb.iterator()
}
class SJIterator[T](private val jit: JavaItr[T]) extends Iterator[T] {
def hasNext: Boolean = jit hasNext
def next: T = jit next
}

Answer 3

Starting Scala 2.13, package scala.jdk.CollectionConverters replaces deprecated packages scala.collection.JavaConverters/JavaConversions:
import scala.jdk.CollectionConverters._
// val javaIterable: java.lang.Iterable[Int] = Iterable(1, 2, 3).asJava
javaIterable.asScala
// Iterable[Int] = List(1, 2, 3)