foreach kotlin waiting for intervals to follow the flow - kotlin

Question

Can someone help me in the following:
I have a FOR and inside it I run some TIMERS
my intention is that initially it runs the TIMER for the first index and only after the timer is canceled does the method go to the next timer. my FOR would need to wait for the TIMER to be finalized.
for (i in 1..3) {
println("running for loop: $i")
val interval: Long = 60 * 1000 * 1 // 1 minute
val timer = Timer("timer: $i", true)
timer.schedule(100, interval) {
println("${LocalTime.now()} to loop: $i")
// some logic here do stop the timer
// if (something happens) timer.cancel()
}
}
my output
running for loop: 1
running for loop: 2
running for loop: 3
18:34:57.147132900 to loop: 2
18:34:57.147132900 to loop: 3
18:34:57.147132900 to loop: 1
18:35:57.137764800 to loop: 3
18:35:57.137764800 to loop: 2
18:35:57.137764800 to loop: 1
etc...
my output as I hope it will be
running for loop: 1
18:34:57.147132900 to loop: 1
18:35:57.147132900 to loop: 1
18:36:57.147132900 to loop: 1
18:37:57.147132900 to loop: 1
running for loop: 2
18:38:57.147132900 to loop: 2
18:39:57.147132900 to loop: 2
running for loop: 3
18:40:57.147132900 to loop: 3
18:41:57.147132900 to loop: 3
18:42:57.147132900 to loop: 3

Answer 1

I have a FOR and inside it I run some TIMERS
This statement is wrong, java.util.Timer is a utility class that can be used to schedule a thread to be executed at certain time in future.
timer.schedule(100, interval) {}
The above line does not block the for loop, the timer is scheduled to be run on the thread and the for loop continues to do next iteration.
You probably need a blocking solution for your purpose of executing them one by one
for (i in 1..3) {
println("running for loop: $i")
val interval: Long = 60 * 1000 * 1 // 1 minute
Thread.sleep(100)
var isRunning = true
while(isRunning) {
println("${LocalTime.now()} to loop: $i")
Thread.sleep(interval)
// some logic here do stop the timer
// if (something happens) isRunning = false
}
}
But probably it isn't the best practise since your thread is just blocked, you could use coroutines to do that without wasting your system resources by blocking threads:
fun main() = runBlocking {
launch {
for (i in 1..3) {
println("running for loop: $i")
val interval: Long = 60 * 1000 * 1 // 1 minute
delay(100)
var isRunning = true
while(isRunning) {
println("${LocalTime.now()} to loop: $i")
delay(interval)
// some logic here do stop the timer
// if (something happens) isRunning = false
}
}
}
// ...
// do sth in main without blocking, these all things run on same thread
// none of the code is blocked
}