MapValue examples for article

Main.scala

import java.util.concurrent.atomic.AtomicInteger

import scala.util.Random

object Main {
  def main(args: Array[String]): Unit = {
    println("Sample1")
    sample1()
    println("Sample2")
    sample2()
    println("Sample3")
    sample3()
    println("Sample4")
    sample4()
    println("Sample5")
    sample5()
  }

  def sample1(): Unit = {
    val someMap = Map("key1" -> "value1", "key2" -> "value2")

    def foo(value: String): String = value + "_changed"

    val resultMap = someMap.map { case (k, v) => k -> foo(v) }
    val resultMapValues = someMap.mapValues(foo)
    println(s"resultMap:       $resultMap")
    println(s"resultMapValues: $resultMapValues")
    println(s"equality: ${resultMap == resultMapValues}")
  }

  def sample2(): Unit = {
    case class ValueHolder(value: String)

    val someMap: Map[String, String] = Map("key1" -> "value1", "key2" -> "value2")

    def foo(value: String): ValueHolder = ValueHolder(value)

    val resultMap: Map[String, ValueHolder] = someMap.map { case (k, v) => k -> foo(v) }
    val resultMapValues: Map[String, ValueHolder] = someMap.mapValues(foo)
    println(s"resultMap:       $resultMap")
    println(s"resultMapValues: $resultMapValues")
    println(s"equality: ${resultMap == resultMapValues}")
  }

  def sample3(): Unit = {
    case class ValueHolder(value: String, seed: Int)

    val someMap = Map("key1" -> "value1", "key2" -> "value2")

    def foo(value: String): ValueHolder = ValueHolder(value, Random.nextInt())

    val resultMap: Map[String, ValueHolder] = someMap.map { case (k, v) => k -> foo(v) }
    val resultMapValues: Map[String, ValueHolder] = someMap.mapValues(foo)
    println(s"resultMap:       $resultMap")
    println(s"resultMapValues: $resultMapValues")
    println(s"equality: ${resultMap == resultMapValues}")

    println(s"simple assert for resultMap:       ${resultMap.head == resultMap.head}")
    println(s"simple assert for resultMapValues: ${resultMapValues.head == resultMapValues.head}")

    println(s"resultMapValues: $resultMapValues")
    println(s"resultMapValues: $resultMapValues")
  }

  def sample4(): Unit = {
    case class ValueHolder(value: String, seed: Int)

    val someMap = Map("key1" -> "value1", "key2" -> "value2")

    def foo(value: String): ValueHolder = ValueHolder(value, Random.nextInt())

    val resultMapValues: Map[String, ValueHolder] = someMap.mapValues(foo).map(identity)
    println(s"resultMapValues: $resultMapValues")

    println(s"simple assert for resultMapValues: ${resultMapValues.head == resultMapValues.head}")

    println(s"resultMapValues: $resultMapValues")
    println(s"resultMapValues: $resultMapValues")
  }

  def sample5(): Unit = {
    val someMap1 = Map("key1" -> new AtomicInteger(0), "key2" -> new AtomicInteger(0))
    val someMap2 = Map("key1" -> new AtomicInteger(0), "key2" -> new AtomicInteger(0))

    def increment(value: AtomicInteger): Int = value.incrementAndGet()

    val resultMap: Map[String, Int] = someMap1.map { case (k, v) => k -> increment(v) }
    val resultMapValues: Map[String, Int] = someMap2.mapValues(increment)
    println(s"resultMap (1):       $resultMap")
    println(s"resultMapValues (1): $resultMapValues")
    println(s"resultMap (2):       $resultMap")
    println(s"resultMapValues (2): $resultMapValues")
  }

}