The sample code to run scala via JSR223 API. I turn usejavacp option true at line 10. Unless that you have to use http://github.com/rjolly/jarlister to list classes in scala-library.jar into MANIFEST.MF of jar that contains this ScalaTest class. I use Scala-2.11.6 to run this code.

ScalaJSR223Test.java

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;

import scala.tools.nsc.interpreter.IMain;
import scala.tools.nsc.settings.MutableSettings.BooleanSetting;

public class ScalaTest {
	public static void main(String[] args) throws Exception{
		ScriptEngine engine = new ScriptEngineManager().getEngineByName("scala");
		((BooleanSetting)(((IMain)engine).settings().usejavacp())).value_$eq(true);
		// or
		// ((scala.tools.nsc.interpreter.IMain)engine).settings().processArgumentString("-usejavacp");
		engine.put("n: Int", 10);
		System.out.println("---");
		engine.eval("1 to n foreach print");
	}
}

@takawitter Thank you very much for this helpful gist! This is the only place I found with details on how to call the Scala script engine from plain Java, rather than from other Scala code. You made all my problems go away: scijava/scripting-scala@1950c73 🍻

Hi,

Using either one of the instructions, I'm getting the following error :

Exception in thread "main" java.lang.ClassCastException: scala.tools.nsc.interpreter.Scripted cannot be cast to scala.tools.nsc.interpreter.IMain
	at TestScala.main(TestScala.java:12)

Any idea why?

@DCransac I'm having this problem too. Appears that there was a change in scripting engine between 2.11 and 2.12.