ObjectProperty.kt

package chap5.CompanionObjects

import atomictest.eq

class WithObjectProperty {
  companion object {
    private var n: Int = 0 // Only one
  }
  fun increment() = ++n
}

fun main() {
  val a = WithObjectProperty()
  val b = WithObjectProperty()
  a.increment() eq 1
  b.increment() eq 2
  a.increment() eq 3
}