Scala autoboxing and Java Map

Question

I have a Java method takes an argument of type Map<Long, Foo>. I am trying to write a unit test for that method in Scala 2.8.1 and pass in a literal Map[Long, Foo].

My code looks like this:

import collection.JavaConversions._
x.javaMethod(asJavaMap(Map(1L -> new Foo, 2L -> new Foo)))

The compiler is giving me the following error:

error: type mismatch;
found   : scala.collection.immutable.Map[scala.Long,Foo]
required: scala.collection.Map[java.lang.Long,Foo]

I also tried it with

import collection.JavaConverters._
x.javaMethod(Map(1L -> new Foo, 2L -> new Foo))

and

import collection.JavaConversions._
x.javaMethod(Map(1L -> new Foo, 2L -> new Foo))

and got the error:

error: type mismatch;
found   : scala.collection.immutable.Map[scala.Long,Foo]
required: java.util.Map[java.lang.Long,Foo]

How do I do this?

Answer 1

The error says that Scala map with scala.Long key type cannot be implicitly converted to Java map based on java.lang.Long:

found   : scala.collection.immutable.Map[scala.Long,Foo]
required: scala.collection.Map[java.lang.Long,Foo]

As a workaround, you may specify the required type manually:

x.javaMethod(asJavaMap(Map((1:java.lang.Long) -> new Foo, (2:java.lang.Long) -> new Foo)))