Can you explain the sharedIn concept and its application?

In Android (and Kotlin Coroutines), sharedIn is an operator that allows converting a cold stream (Flow) into a hot, shared stream among multiple subscribers.

When you have a Flow that performs some work upon subscription, sharedIn lets you run that work once and share the result among all subscribers, avoiding repeated computations.

Example of usage:

val flow = flow {
    emit(fetchData()) // Long operation
}.shareIn(scope = coroutineScope, started = SharingStarted.Lazily, replay = 1)

// Multiple subscribers will receive the same data without calling fetchData() again
flow.collect { data -> println(data) }
flow.collect { data -> println(data) }

Thus, sharedIn is useful for optimization and preventing redundant calculations when working with data streams in Android applications.