How can i compile java record with scala code?

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I'm currently working on project with both Scala and Java. And we want to rewrite some Scala code on Java. So when I've been starting rewrite my code I've faced with this issue.

CountryResponse.java:5: illegal start of type declaration

It seem like Scala couldn't compile Java's records introduced in JDK 16. I've made some research and found only this discussion on GitHub. Could someone suggest any workaround to compile Java's records?

I did try increase Scala version from 2.12.2 to 2.13.6 but problem wasn't solved.

We use Java 16, Scala 2.12.2 and Gradle 7.0.1 and also scala and java plugins for Gradle.

Also here my gradle's settings for compile both sources.

compileScala {
    sourceCompatibility("16")
    targetCompatibility("16")
}

sourceSets {
    main {
        java {
            srcDirs = []
        }
        scala {
            srcDirs = ['src/main/scala', 'src/main/java']
        }
    }
}

edit: update link to discussion

gradle scala java
1 Answers

I tested with following project containing both Scala and Java 16 sources. The Scala and Java source depends on each other.

If your both Java and Scala sources depend on each other, then you will need to put those sources under common folder. Lets say main/jvm.

You can place all your Java records under main/java. This will work as long as your records don't have dependency on Scala code. Otherwise you will have to break this into multiple modules and micromanage according to the dependency graph.

Gradle version is 7.1, and this project builds and then runs successfully (both ScalaMain and JavaMain).

build.gradle

plugins {
    id 'java'
    id 'scala'
}

group 'org.example'
version '1.0-SNAPSHOT'

repositories {
    mavenCentral()
}

compileScala {
    sourceCompatibility("16")
    targetCompatibility("16")
}

sourceSets {
    main {
        java {
            srcDirs = ['src/main/java']
        }
        scala {
            srcDirs = ['src/main/jvm']
        }
    }
}

dependencies {
    implementation 'org.scala-lang:scala-library:2.13.6'
}

main/java/TestJavaRecord.java

public record TestJavaRecord(int i) {}

main/jvm/TestScalaClass.scala

class TestScalaClass(val i: Int, val testJavaRecord: TestJavaRecord) {}

main/jvm/TestJavaClass.java

public class TestJavaClass {
    public int i;
    public TestScalaClass testScalaClass;

    public TestJavaClass(int i, TestScalaClass testScalaClass) {
        this.i = i;
        this.testScalaClass = testScalaClass;
    }
}

main/jvm/ScalaMain.scala

object ScalaMain extends App {

  val testJavaRecord = new TestJavaRecord(5)

  val testScalaClass = new TestScalaClass(5, testJavaRecord)

  val testJavaClass = new TestJavaClass(5, testScalaClass)

  println(testJavaRecord.i)

  println(testScalaClass.testJavaRecord.i)

  println(testJavaClass.testScalaClass.testJavaRecord.i)

}

main/jvm/JavaMain.java

public class JavaMain {

    public static void main(String[] args) {
        TestJavaRecord testJavaRecord = new TestJavaRecord(5);

        TestScalaClass testScalaClass = new TestScalaClass(5, testJavaRecord);

        TestJavaClass testJavaClass = new TestJavaClass(5, testScalaClass);

        System.out.println(testJavaRecord.i());

        System.out.println(testScalaClass.testJavaRecord().i());

        System.out.println(testJavaClass.testScalaClass.testJavaRecord().i());
    }
}
user_11519290
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