Challenge 1: Lazy Initialization — Solution

class DataLoader {
    val expensiveData: List<Int> by lazy {
        println("Loading data...")
        listOf(1, 2, 3, 4, 5)
    }
}

fun main() {
    val loader = DataLoader()
    println("Loader created")

    println(loader.expensiveData)
    println(loader.expensiveData)
}

/*
Output:
Loader created
Loading data...
[1, 2, 3, 4, 5]
[1, 2, 3, 4, 5]

Notes:
- "Loader created" prints before "Loading data..." — proof that the lazy
  block hasn't run yet at construction time.
- "Loading data..." only prints once, on the first access to
  expensiveData. The second access reuses the cached result without
  running the block again.
- If expensiveData were never accessed at all, "Loading data..." would
  never print — the whole point of lazy is paying the cost only when
  actually needed.
*/