thread safe

Main.kt

val formatter by safeThread {
  SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss:SSS'Z'", Locale.getDefault())
}

fun main(): Unit = runBlocking {
  val time = "2024-01-24T22:58:54:322Z"

  launch {
    launch {
      withContext(Dispatchers.Default) {
        repeat(1000) {
          println(formatter.parse(time)?.time)
        }
      }
    }
    launch {
      withContext(Dispatchers.Default) {
        repeat(1000) {
          println(formatter.parse(time)?.time)
        }
      }
    }
    launch {
      withContext(Dispatchers.Default) {
        repeat(1000) {
          println(formatter.parse(time)?.time)
        }
      }
    }
  }
}

SafeThread.kt

class SafeThreadLazy<T>(val provider: () -> T) : Lazy<T> {
  private val threadLocal = object : ThreadLocal<Lazy<T>>() {
    override fun initialValue(): Lazy<T> = lazy(LazyThreadSafetyMode.NONE, provider)
  }

  override val value get() = threadLocal.get()!!.value
  override fun isInitialized() = threadLocal.get()!!.isInitialized()
}

fun <T> safeThread(provider: () -> T) = SafeThreadLazy(provider)