Override a java method that expects a double array

Question

Say I define the following java interface: ``` public interface A { public Double[] x(); } ``` And then try to implement it in scala as follows: ``` class B extends A { val v: Array[Double] = Array(2.3, 6.7) override def x() = v } ``` The compiler gives me the following error: ``` type mismatch; [error] found : Array[scala.Double] [error] required: Array[java.lang.Double] [error] override def x() = v ``` Can someone tell me the recommended way to automatically convert this array? Thanks Des

Accepted Answer

You can't convert it automatically. The issue is that `Double` in Java means the class `java.lang.Double` (while in Scala it means `scala.Double` which is mostly the same as `double` in Java), and so the overriding method has to return `Array[java.lang.Double]`. If you have an `Array[Double]`, you can convert it using `map`:

```
val v: Array[Double] = ...
val v1 = v.map(java.lang.Double.valueOf(_)) // valueOf converts Double into java.lang.Double
```

You could make this conversion implicit:

```
implicit def wrapDoubleArray(arr: Array[Double]): Array[java.lang.Double] =
  arr.map(java.lang.Double.valueOf(_))
```

but this is a bad idea in most circumstances.

Override a java method that expects a double array

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