Utility to generate array expression using Java API for JSON Processing

build.gradle

dependencies {
    implementation "org.glassfish:javax.json:1.1.4"
    testCompile group: 'org.junit.jupiter', name: 'junit-jupiter-api', version: '5.5.2'
    testCompile group: 'org.junit.jupiter', name: 'junit-jupiter-engine', version: '5.5.2'
    testCompile group: 'org.junit.jupiter', name: 'junit-jupiter-params', version: '5.5.2'
    testCompile group: 'org.assertj', name: 'assertj-core', version: '3.13.2'
}

JsonUtil.kt

package kazusato.util

import javax.json.Json

object JsonUtil {

    fun toJsonArray(stringList: List<String>): String {
        val arrayBuilder = Json.createArrayBuilder()
        stringList.forEach { str ->
            arrayBuilder.add(str)
        }
        val arrayObj = arrayBuilder.build()

        return arrayObj.toString()
    }

}

JsonUtilTest.kt

package kazusato.util

import org.assertj.core.api.Assertions.assertThat
import org.junit.jupiter.api.Test

class JsonUtilTest {

    @Test
    fun testToJsonArray() {
        val list = listOf("AAA", "BBB", "CCC")
        val result = JsonUtil.toJsonArray(list)
        assertThat(result).isEqualTo("""["AAA","BBB","CCC"]""")
    }

}