Doing math operations on Scala objects in Java code

Question

In my java code I am using a method, let's call foo(), that returns a scala.Double[].

scala.Double[] arr = foo();

I want to sum up arr into a scala.Double, but am having trouble. I've found that doing any kind of math operation on scala.Doubles gets me an error message from my IDE:

arr[0] + arr[1];
arr[0] * arr[1];
//etc

get me messages like

Operator '+' cannot be applied to 'scala.Double', 'scala.Double'

How can I do math operations on scala.Doubles within java code? (alternatively, is there another way to sum up a scala.Double[] within java code?)

Dmytro Mitin · Accepted Answer · 2020-04-13 21:42:50Z

0

It's not clear how you got scala.Double[] in Java. If you have Array[Double] in Scala, it's seen in Java as double[], not scala.Double[].

Anyway, if you have scala.Double[] in Java

public class App {
  public static scala.Double[] arr = foo();
}

then it's seen in Scala also as Array[scala.Double]

object App1 {
  val arr1: Array[Double] = App.arr
}

and then the latter is seen back in Java as double[]

public class App {
  public static scala.Double[] arr = foo();
  public static double[] arr2 = App1.arr1();
}

Then you can do arr2[0] + arr2[1], arr2[0] * arr2[1]...

edited Apr 13, 2020 at 21:42

answered Apr 13, 2020 at 21:35

Dmytro Mitin

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