build.gradle.kts

/*
 * This file was generated by the Gradle 'init' task.
 *
 * This generated file contains a sample Scala library project to get you started.
 * For more details take a look at the Scala plugin chapter in the Gradle
 * user guide available at https://docs.gradle.org/5.0/userguide/scala_plugin.html
 */
import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar

plugins {
    // Apply the scala plugin to add support for Scala
    id("scala")
    id("application")
    id("com.github.johnrengelman.shadow") version "5.0.0"
}

repositories {
    // Use jcenter for resolving your dependencies.
    // You can declare any Maven/Ivy/file repository here.
    jcenter()
}

dependencies {
    // Use Scala 2.12 in our library project
    implementation("org.scala-lang:scala-library:2.12.7")
    implementation("com.ibm.icu:icu4j:63.1")

    // Use Scalatest for testing our library
    testImplementation("junit:junit:4.12")
    testImplementation("org.scalatest:scalatest_2.12:3.0.5")

    // Need scala-xml at test runtime
    testRuntimeOnly("org.scala-lang.modules:scala-xml_2.12:1.1.1")
}

application {
    // Define the main class for the application
    mainClassName = "KatakanaRomajiConvert.Main"
}

tasks.withType<Jar> {
    manifest {
        attributes(mapOf(
                "Main-Class" to "KatakanaRomajiConvert.Main"
        ))
    }
}

tasks.withType<ShadowJar> {
    baseName = "kana2romaji"
    classifier = ""
    version = ""
}

gradle.properties

org.gradle.jvmargs='-Dfile.encoding=UTF-8'
org.gradle.daemon=true
// org.gradle.java.home=C:\\JDKPortable
// systemProp.http.proxyHost=
// systemProp.http.proxyPort=
// systemProp.https.proxyHost=
// systemProp.https.proxyPort=

Main.scala

package KatakanaRomajiConvert

import com.ibm.icu.text.Transliterator

class KatakanaRomajiConvert(val word: String = "") {
  private val transliterator = Transliterator.getInstance("Katakana-Latin")
  def toRomaji: String = {
    val kana: Option[String] = Some(word)
    transliterator.transliterate(kana.getOrElse(""))
  }
}

object Main extends App {
  if (args.length != 0) {
    val katakana: String = args(0)
    val katakanaObj = new KatakanaRomajiConvert(katakana)
    println(katakanaObj.toRomaji)
  } else {
    println("")
  }
}

MainSpec.scala

package KatakanaRomajiConvert

import org.scalatest._

class KatakanaRomajiConvertSpec extends FlatSpec with Matchers {
  "Input strings \"トウキョウ\"" should "output strings toukyou" in {
    new KatakanaRomajiConvert("トウキョウ").toRomaji shouldEqual "toukyou"
  }
  "Input no string" should "" in {
    new KatakanaRomajiConvert("").toRomaji shouldEqual ""
  }
  "Argument is null" should "" in {
    new KatakanaRomajiConvert(null).toRomaji shouldEqual ""
  }
  "No argument" should "" in {
    new KatakanaRomajiConvert().toRomaji shouldEqual ""
  }
  "Input strings \"あいうアイウabcＡＢＣ\"" should "" in {
    new KatakanaRomajiConvert("あいうアイウabcＡＢＣ").toRomaji shouldEqual "あいうaiuabcＡＢＣ"
  }
  "Input strings \"あいう アイウ abc ＡＢＣ\"" should "" in {
    new KatakanaRomajiConvert("あいう アイウ abc ＡＢＣ").toRomaji shouldEqual "あいう aiu abc ＡＢＣ"
  }
}