Create CLI App

.gitignore

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+*.class
+*.log
+
+# sbt specific
+.cache
+.history
+.lib
+dist/*
+target/
+lib_managed/
+src_managed/
+project/boot/
+project/plugins/project/
+
+# Scala-IDE specific
+.scala_dependencies
+.worksheet
+.idea

scala_cli_app/build.sbt

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+name := "scala_cli_app"
+
+version := "1.0"
+
+scalaVersion := "2.12.10"
+
+libraryDependencies += "org.scalatest" %% "scalatest" % "3.0.8" % "test"

scala_cli_app/project/build.properties

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+sbt.version=1.3.5

scala_cli_app/src/main/scala/app/CLIApp.scala

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+package app
+
+import util.DateUtil
+import scala.annotation.tailrec
+import scala.io.StdIn.readLine
+import scala.util.{Success, Try}
+
+object CLIApp extends App {
+  val date1 = DateUtil.str2Date(getInput)
+  val date2 = DateUtil.str2Date(getInput)
+  println(s"date1: ${DateUtil.date2Str(date1)}")
+  println(s"date2: ${DateUtil.date2Str(date2)}")
+  println(s"yearsBetween: ${DateUtil.yearsBetween(date1, date2)}")
+  println(s"compare     : ${DateUtil.compare(date1, date2)}")
+
+  @tailrec
+  def getInput: String = {
+    println("入力してください (例: 2020-01-01)")
+    val input = readLine()
+
+    Try(DateUtil.str2Date(input)) match {
+      case Success(_) => input
+      case _          => getInput
+    }
+  }
+}

scala_cli_app/src/main/scala/util/DateUtil.scala

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+package util
+
+import java.time.{LocalDate, LocalDateTime}
+import java.time.format.{DateTimeFormatter, ResolverStyle}
+import java.time.temporal.ChronoUnit.YEARS
+
+object DateUtil {
+  private val dateFormatter =
+    DateTimeFormatter.ofPattern("uuuu-MM-dd")
+      .withResolverStyle(ResolverStyle.STRICT)
+
+  private val dateTimeFormatter =
+    DateTimeFormatter.ofPattern("uuuu-MM-dd HH:mm")
+      .withResolverStyle(ResolverStyle.STRICT)
+
+  def str2Date(str: String): LocalDate = {
+    LocalDate.parse(str, dateFormatter)
+  }
+
+  def str2DateTime(str: String): LocalDateTime = {
+    LocalDateTime.parse(str, dateTimeFormatter)
+  }
+
+  def date2Str(date: LocalDate): String = {
+    date.format(dateFormatter)
+  }
+
+  def dateTime2Str(date: LocalDateTime): String = {
+    date.format(dateTimeFormatter)
+  }
+
+  def yearsBetween(localDate1: LocalDate, localDate2: LocalDate): Int = {
+    YEARS.between(localDate1, localDate2).toInt
+  }
+
+  def compare(localDate1: LocalDate, localDate2: LocalDate): Int = {
+    localDate1.compareTo(localDate2).abs
+  }
+}

scala_cli_app/src/test/scala/util/DateUtilSpec.scala

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+package util
+
+import java.time.{LocalDate, LocalDateTime}
+import org.scalatest.{FunSpec, Matchers}
+
+class DateUtilSpec extends FunSpec with Matchers{
+  describe("str2Date") {
+    it("String => LocalDate") {
+      val expected = LocalDate.of(2020, 1, 1)
+      DateUtil.str2Date("2020-01-01") shouldEqual expected
+    }
+  }
+
+  describe("str2DateTime") {
+    it("String => LocalDateTime") {
+      val expected = LocalDateTime.of(2020, 1, 1, 0, 30, 0)
+      DateUtil.str2DateTime("2020-01-01 00:30") shouldEqual expected
+    }
+  }
+
+  describe("date2Str") {
+    it("LocalDate => String") {
+      val input = LocalDate.of(2020, 1, 1)
+      DateUtil.date2Str(input) shouldEqual "2020-01-01"
+    }
+  }
+
+  describe("dateTime2Str") {
+    it("LocalDate => String") {
+      val input = LocalDateTime.of(2020, 1, 1, 0, 30, 0)
+      DateUtil.dateTime2Str(input) shouldEqual "2020-01-01 00:30"
+    }
+  }
+
+  describe("yearsBetween") {
+    it("calculate age") {
+      val input1 = LocalDate.of(2018, 4, 1)
+      val input2 = LocalDate.of(2020, 1, 1)
+      DateUtil.yearsBetween(input1, input2) shouldEqual 1
+    }
+  }
+
+  describe("compare") {
+    it("calculate age") {
+      val input1 = LocalDate.of(2018, 4, 1)
+      val input2 = LocalDate.of(2020, 1, 1)
+      DateUtil.compare(input1, input2) shouldEqual 2
+    }
+  }
+}