Using Scala from Java: passing functions as parameters

Question

Consider the following Scala code:

package scala_java
object MyScala {
  def setFunc(func: Int => String) {
    func(10)
  }
}

Now in Java, I would have liked to use MyScala as:

package scala_java;
public class MyJava {
    public static void main(String [] args) {
        MyScala.setFunc(myFunc);  // This line gives an error
    }
    public static String myFunc(int someInt) {
        return String.valueOf(someInt);
    }
}

However, the above does not work (as expected since Java does not allow functional programming). What is the easiest workaround to pass a function in Java? I would like a generic solution that works with functions having arbitrary number of parameters.

EDIT: Does Java 8 have any better syntax than the classic solutions discussed below?

Answer 1

In the scala.runtime package, there are abstract classes named AbstractFunction1 and so on for other arities. To use them from Java you only need to override apply, like this:

Function1<Integer, String> f = new AbstractFunction1<Integer, String>() {
    public String apply(Integer someInt) {
        return myFunc(someInt);
    }
};

If you're on Java 8 and want to use Java 8 lambda syntax for this, check out https://github.com/scala/scala-java8-compat.