Converting Scala array of Int to Java array of Integer

Question

How to convert Scala Array[Int] to Java Integer[]? It seems that the default is to convert int to int[] and that's not a proper argument for method defined as

public static <T extends Comparable<? super T>> T[] merge(T[] xs)

Compiling fails with the following error

type mismatch;
 found   : Array[Int]
 required: Array[? with Object]
Note: Int >: ? with Object, but class Array is invariant in type T.
You may wish to investigate a wildcard type such as `_ >: ? with Object`. (SLS 3.2.10)
      val res = SimpleSort.merge(xs)

                             ^

scand1sk · Accepted Answer · 2013-09-19 11:02:56Z

5

Maybe with:

val javaArray: Array[java.lang.Integer] = scalaArray map java.lang.Integer.valueOf

AFAIK, it is not a good practice in java to manipulate array of objects, you should use Lists instead. BTW, your merge method will have trouble instantiating the array of T.

edited Sep 19, 2013 at 11:02

answered Sep 19, 2013 at 10:55

scand1sk

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5 Comments

Chirlo Over a year ago

This converts to an scala Array[Integer] not a java Integer[]

scand1sk Over a year ago

Scala's Array[Integer] and Java's Integer[] should be exactly the same.

scand1sk Over a year ago

I just tested my solution: it compiles.

Chirlo Over a year ago

Just checked, you're right. BTW, I also found there's a method Int.box on scala's Int which boxex an Int to an Integer, so you can rewrite as scalaArray.map(Int.box)

Luigi Plinge Over a year ago

Or you could take advantage of the implicit conversion from Int to Integer with scalaArray map (x => x: Integer)

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