using Java generic method from Scala

Question

I'm having problem understanding Scalac's error message in this example: Bean.java ``` public class Bean { static public class Attribute { public final String name; public Attribute(String name) {this.name = name;} // equals and hashcode omitted for simplicity } public void set(Attribute attribute, T value) {} public static Attribute AGE = new Attribute("age"); } ``` Test.scala ``` object Test { def test() { val bean = new Bean(); bean.set(Bean.AGE, 2L); } } ``` compiling yeilds this (tried with scalac 2.9.2): ``` Test.scala:4: error: type mismatch; found : Bean.Attribute[java.lang.Long] required: Bean.Attribute[Any] Note: java.lang.Long <: Any, but Java-defined class Attribute is invariant in type T. You may wish to investigate a wildcard type such as `_ <: Any`. (SLS 3.2.10) bean.set(Bean.AGE, 2L); ^ one error found ``` why is it requiring Attribute[Any]? Doing same in Java works fine thanks

Accepted Answer

The error is due to mismatch between `java.lang.Long` and scala `Long`.

`Bean.AGE` is of type `Bean.Attribute[java.lang.Long]`. Hence the scala compiler expects a `java.lang.Long` as the other argument. But you are passing is `2L` which is `scala.Long` and not `java.lang.Long`. Hence it shows error.

Doing this will work as expected:

```
 b.set(Bean.AGE,new java.lang.Long(23))
```

Thanks to @senia, the below is a better alternative:

```
bean.set[java.lang.Long](Bean.AGE, 23)
bean.set(Bean.AGE, 23:java.lang.Long)
```

using Java generic method from Scala

Solution

Problem