Access inner class method with "fine" syntax in Java using Scala class & object

Question

I have the following scala example:

class Nested {}
object Nested {
  class Inner {}
  object Inner {
    def x = 321
  }
}

With a JUnit test to test specifically that I can do Nested.Inner.x() and call the method freely without the Nested.Inner$.MODULE$.x():

  import static junit.framework.Assert.*;
  import org.junit.Test;

  public class TestFromJava {

  @Test
  public void accessTest() {
    assertEquals(321, Nested.Inner.x());
  }
}

This compiles, but at the moment of running the test, I am getting (sbt test):

[error] TestFromJava.java:8: cannot find symbol
[error]   symbol:   method x()
[error]   location: class Nested.Inner
[error] Nested.Inner.x

How can I benefit from both Scala syntax and not using the horrible $? Maybe it is a feature of the language as how it generates the object instances.

What do you mean by "this compiles"? Is that a runtime error you are showing? Looks like you are using sbt. Did you succeed to run sbt test:compile? I think you pretty much do need to access that symbol through Nested.Inner$.MODULE$.x() — 0__
– 0__, Commented Feb 29, 2016 at 20:49
But where is TestFromJava, is that main sources or test sources? Is that in src/main/java or src/test/java (assuming you have an sbt build - can you confirm this?). compile does not compile test-sources, it's short for compile:compile. You need to run test:compile. — 0__
– 0__, Commented Feb 29, 2016 at 21:03
Which scala version is this? If I recall you don't need the $MODULE for 2.11. — yw3410
– yw3410, Commented Feb 29, 2016 at 21:45
@0__ on sbt test:compile it complains about the same compilation error from above. @yw3410 2.11.7 scala version — Tomás Duhourq
– Tomás Duhourq, Commented Mar 1, 2016 at 12:41

0__ · Accepted Answer · 2016-03-01 14:04:56Z

1

You have to qualify singleton object access when calling from Java, as explained in this question.

In your case that would be

Nested.Inner$.MODULE$.x()

answered Mar 1, 2016 at 14:04

0__

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