Is it good idea to use atomic boolean in kotlin?

Question

Hey I am learning in atomic in kotlin. I am wondering is this good idea to use atomic boolean in my scenario? Can someone suggest, how to do in atomic way.

Scenario 1 Not for first time call

var isFirstTime = true

fun notForFirstTime(){
   if(!isFirstTime){
     jobDone()
   }
  isFirstTime = false
}

Scenario 2 only for first time

var isFirstTime = true

fun onlyForFirstTime(){
   if(isFirstTime){
     jobDone()
   }
  isFirstTime = false
}

Can I do this in atomic way? Also is this good idea?

Answer 1

It depends on what you're trying to achieve.

For scenario 2, most of the time what you want is a value that's computed once and reused later. For this use-case, you can use lazy delegates like this:

class MyClass {
    
    // will be computed the first time it's accessed, and then reused
    val value by lazy { computeExpensiveValue() }
}


fun computeExpensiveValue(): Int {
    // some complex stuff
    return 42
}

I never encountered scenario 1, but in cases where lazy is not sufficient you could indeed use atomic booleans for CAS approaches, or locks. Check for instance kotlinx.atomicfu.

If you're using Kotlin coroutines, you might want to check other synchronization primitives like Mutex and Semaphore. But in general it's preferable to make coroutines communicate over channels rather than sharing mutable state.