I'm looking for a simple and elegant way to convert Java Comparator to scala Ordering.
Use case:
I have a Scala collection that I want to sort using a comparator defined in Java code:
val comparator = getComparator()
val collection = Seq("a","b")
collection.sorted(???)
There is already an implicit conversion in the standard library: scala.math.Ordering.comparatorToOrdering
You just need an import to use it:
import scala.math.Ordering.comparatorToOrdering
val comparator = getComparator()
val collection = Seq("a","b")
collection.sorted(comparator)
If I am not mistaken, the Ordering companion contains an implicit conversion from Comparable[A] to Ordering[A]:
You can import scala.math.Ordering.Implicits to gain access to other implicit orderings.
Example:
import java.util.Date
val dateOrdering = implicitly[Ordering[Date]]
import dateOrdering._
val now = new Date
val later = new Date(now.getTime + 1000L)
now < later ... should be true
Ordering.comparatorToOrdering method so you don't need to make one yourself as @Harper does, just import it. See scala-lang.org/api/2.12.0/scala/math/…The best way I have found so far is to define your own implicit conversion between java.util.Comparator and Ordering
implicit def comparatorToOrdering[T](comparator: Comparator[T]) =
new Ordering[T] {
def compare(x: T, y: T): Int = comparator.compare(x, y)
}
Import this and then you can write
val comparator = getComparator()
val collection = Seq("a","b")
collection.sorted(comparator)