Add Scala operators to final Java class

Question

I am using the jMonkeyEngine (Java Game Engine) in Scala, which works out pretty well so far, but now I am asking myself whether there is an elegant way of overloading operators for the `Vector3f` (and similar) classes. My first idea was to inherit from `Vector3f` and overload the operators, but `Vector3f` is final, so that is not an option. Next I thought maybe I could have a singleton/scala object with static methods that operate on `Vector3f`, like below, but that does not work either: ``` object VectorMath { def *(factor: Float, vector: Vector3f) = vector.mult(factor) } //and then somewhere import VectorMath._ var v = new Vector3f(1,2,3); var u = 1.2f * v; //this does not work, because Float does not have * overloaded for Vector3f var u = VectorMath.*(1.2f, v); //this does work, but defeats the purpose ``` So all I can think of now is to wrap the Vector3f in a new Scala class and delegate the operator calls to the appropriate Java methods. This has, however, three downsides: - I w…

Accepted Answer

Or is there maybe a Scala syntax that I don't know of to do these kinds of things?

Yeah, there are implicits:

```
class VectorMath(f: Float) { def * (v: Vector3f) = v mult f }
implicit def VectorMath(f: Float) = new VectorMath(f)

val v = new Vector3f(1,2,3)
1.2F * v
// treated as: VectorMath(1.2F).*(v)
```

Since Scala 2.10 the implicit conversion can also be written as:

```
implicit class VectorMath(f: Float) { def * (v: Vector3f) = v mult f }
```

Since 2.10 there are also value classes which are optimized by the compiler to get better performance:

```
implicit class VectorMath(val f: Float) extends AnyVal { def * (v: Vector3f) = v mult f }
```

Add Scala operators to final Java class

Solution

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