Play 2.4 - Can't convert a java Set to a Scala.collection.immutable.Set

[Tiago Lourenço]

I'm new in play and I'm following the book "Play for Java MEAP v2". 

I'm stuck in page 48, where a can't convert a java Set to a Scala.collection.immutable.Set, I have the follow error: 


" render(scala.collection.immutable.list<models.Product>) in canot be applied to java.util.list<models.Product>"


I need help please :)

[amertum]

For mutable collection, you can use the class scala.collection.JavaConverters which have methods like asScalaSetConverter.

For immutable collection, there is also the play class play.libs.Scala.

Class as scala.collection.immutable.Set$.MODULE provide methods to create immutable Set. Following this pattern, the class scala.collection.immutable.Map$.MODULE exists also.

This is the bad side of integrating Scala into Java. It is easier the other way.

[Tiago Lourenço]

Can give me one example more specific, please 

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[ludo amertum]

java.util.Set<String> javaSet = new java.util.HashSet<>();

scala.collection.mutable.Set<String> mutableScalaSet = scala.collection.JavaConverters.asScalaSetConverter(javaSet).asScala();

scala.collection.immutable.Set<String> immutableScalaSet = mutableScalaSet.toSet();

[Tiago Lourenço]

Thanks, very much :) amertum

[Tiago Lourenço]

Hi, 

I have the follow problem:

" render(play.api.Data.Form<models.Product>) in canot be applied to play.Data.Form<models.Product>"

How can I resolve this????

[Pablo Fernandez]

Can you give us more context? Usually when you have a play.api.Something and play.Something mismatch it has to do with a Java/Scala incompatibility.

Joining the dots with your initial question... perhaps you're configuring your play project to be a Java project and using Scala?