How to import scala class into IntelliJ IDEA

Question

I know this might not sound intelligent, but I am new to this and I really want to figure it out. I have been coding in JAVA recently and on the other hand have some function implemented within scala. I came across this article:

Interop Between Java and Scala

Which says it is possible to mix JAVA and scala. Since I am coding in IntelliJ IDEA, am wondering if there is anyway to bring in scala classes and use them within my JAVA code?

I have already included scala-library.jar using:

<dependency>
    <groupId>org.scala-lang</groupId>
    <artifactId>scala-library</artifactId>
    <version>2.10.3</version>
</dependency>

Any help or direction toward other useful links is much appreciated. Thanks.

Answer 1

• if there is anyway to bring in scala classes and use them within my Java code?
• is it possible to use scala classes inside Java or there is no way at all?

Yes and yes. There are two scenarios: First you have an existing Scala library, then you can just use it in your existing Maven build as you have shown with the standard Scala library. Second (and I assume that is your actual question?) you have a project which contains both Java and Scala source code . In that case you need to compile both types of source files.

In IntelliJ that would require that you somehow add the Scala façade to your project. Unfortunately, I am not a Maven expert, so I cannot tell you how this works with a Maven build.

But if you use sbt and an sbt-based IntelliJ project , then IntelliJ will build the entire project with an sbt build server which is capable of compiling both your Java and Scala sources.

You would have a directory structure like this:

project
  build.properties
build.sbt
src
  main
    scala
      foo
        Foo.scala
    java
      foo
        Bar.java

For example as build.properties :

sbt.version=0.13.11

As build.sbt :

scalaVersion := "2.11.8"

As Foo.scala :

package foo

class Foo {
  def test(): Unit = println("Hello from Scala!")
}

And as Bar.java :

package foo;

public class Bar {
    public static void main(String[] args) {
        final Foo f = new Foo();
        f.test();
    }
}

Answer 2

To complete user 0__ post, if you are using Maven build, based on the following link:

Snippet: Mixing Scala, Java in a Maven Project

You will need to make some change in pom.xml file. Under dependencies add:

<dependency>
    <groupId>org.scala-lang</groupId>
    <artifactId>scala-library</artifactId>
    <version>2.10.3</version>
</dependency>

Also, under plugins you need to add the following:

<plugin>
    <groupId>org.scala-tools</groupId>
    <artifactId>maven-scala-plugin</artifactId>
    <version>2.9.1</version>
</plugin>

Finally, under repositories:

<repository>
     <id>scala-tools.org</id>
     <name>Scala-tools Maven2 Repository</name>
     <url>http://scala-tools.org/repo-releases</url>
</repository>

Now, if you just add a new .scala file which includes you scala class, IntelliJ IDEA will detect that it is scala and will add other necessary plugins and JDK for it. If the two files (.java and .scala) are within the same project, you can easily access them from each other. More details could be found here:

Can we write Scala code inside a Java program?