Scala Array[String] to Java String varargs

Question

I have some Scala code that needs to call a Java 7 method that is defined as follows:

public void addListener(InputListener listener, String... mappingNames) {
    <details omitted here for brevity>
}

Here is my Scala code that call addListener:

inputManager.addListener(myListener, getActionInputs())

// Then the getActionInputs method:
def getActionInputs() : Array[String] = {
  Array("Red", "Fruit", "Cow")
}

This yields a compiler error:

Type mistmatch, expected: String, actual: Array[String]

I tried importing the Java/Scala conversions classes to convert my Scala Array[String] to a Java array, but have not been successful. Any ideas as to what the fix is?

Yuval Itzchakov · Accepted Answer · 2017-03-20 15:30:56Z

9

You need to add :_* to transform the Array[String] to varargs:

Java:

public class C {
    public void addListener(String... mappingNames) {
        System.out.println(Arrays.toString(mappingNames));
    }
}

Scala:

def main(args: Array[String]): Unit = {
  val c = new C
  c.addListener(Array("a", "b", "c") :_*)
}

Yields:

[a, b, c]

edited Mar 20, 2017 at 15:30

answered Mar 20, 2017 at 15:19

Yuval Itzchakov

150k32 gold badges276 silver badges333 bronze badges

Sign up to request clarification or add additional context in comments.

7 Comments

Jasper-M Over a year ago

Isn't that only for Scala varargs?

Jasper-M Over a year ago

It appears you're right. I don't think that always used to be the case. Is this new since 2.12?

Yuval Itzchakov Over a year ago

@Jasper-M I ran this on 2.11.8

Jasper-M Over a year ago

Yes, it seems to have always been like that. Now I wonder why I thought it wasn't...

Yuval Itzchakov Over a year ago

@Jasper-M The oldest I found is a forum question from 2010 with Scala 2.8.0 claiming this works.

|

Collectives™ on Stack Overflow

Scala Array[String] to Java String varargs

1 Answer 1

7 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

7 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related