Java/Scala Required: Iterable[_ <: Float], found: Iterable[Float]-CodePudding

I have a protobuf method in Java with definition

public Builder addAllTensor(
          Iterable<? extends Float> values)

I call the method in Scala with a val a: ArrayList[Float], its ok during code check, but error during build

type mismatch;
 found   : java.util.ArrayList[scala.Float]
 required: Iterable[_ <: java.lang.Float]

But calling it with a.toIterable it raises error in code check(in IntelliJ IDEA)

Required: Iterable[_ <: Float], found: Iterable[Float]

(How could this be type mismatch...) Just wonder why...

CodePudding user response：

The issue is with the scala.Float versus Java's Float.

Automatic conversion doesn't happen inside collections, you have to create somehow a collection of Java's Float.