Call java function which takes double[] as parameter

Question

I am interfacing with a Java library which takes in a double[] as parameter and add elements to the array. I tried creating a Scala mutable array with JavaConversions but it is not able to manage this conversion. Any ideas?

Java:

 public static double libraryFn(double[] numbers) {
    .....
    numbers[0] = 1.0
 }

Scala:

def caller() {
     // Does not work
     val myNumbers =  new Array[java.lang.Double](1)
    libraryFn(myNumbers)
 }

Thanks for the responses. Looking at the library source more closely, it looks like the library has a bug and was not a scala/java issue at all.

Use Array[java.lang.Double] stackoverflow.com/questions/3940699/passing-java-array-to-scala — Ashalynd
– Ashalynd, Commented Oct 25, 2013 at 0:35
That question is about calling a scala function with Java array. More importantly there is no issue with mutability. What I have is a java function that takes in a double[] and adds a number to the array (out parameter). — Parag
– Parag, Commented Oct 25, 2013 at 0:46
java.lang.Double is not Java's double. It needs to be Array[Double], in Scala. — Daniel C. Sobral
– Daniel C. Sobral, Commented Oct 25, 2013 at 6:28

Daniel C. Sobral · Accepted Answer · 2013-10-25 00:46:54Z

5

I wonder what is this mutable array you speak of. Just use Array[Double] -- that is the Java double[].

answered Oct 25, 2013 at 0:46

Daniel C. Sobral

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2 Comments

Parag Over a year ago

val myNumbers = Array[Double](10); libraryFn(myNumbers) throws java.lang.ArrayIndexOutOfBoundsException.

Daniel C. Sobral Over a year ago

@Parag That's an issue with the array size, not with its type. Also, Array[Double](10) creates an array size 1 with 10.0 as its single element. If you want an array of size 10, you should do new Array[Double](10), or use Array.fill or similar methods.

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