【Kotlin/Android】AtomicIntegerでスレッドセーフにカウンターを扱う方法

var counter = 0

val threads = List(100) {
    thread {
        repeat(1000) {
            counter++
        }
    }
}

threads.forEach { it.join() }

println("Final counter value: $counter")
// Final counter value: 98298

val counter = AtomicInteger(0)

val threads = List(100) {
    thread {
        repeat(1000) {
            counter.incrementAndGet()
        }
    }
}

threads.forEach { it.join() }

println("Final counter value: ${counter.get()}")
// Final counter value: 100000

val counter = AtomicInteger(0)

val count = counter.get()

counter.set(10)

val count = counter.incrementAndGet()

val count = counter.decrementAndGet()

val count = counter.addAndGet(4)

val wasUpdated = counter.compareAndSet(15, 20)

var counter = 0
val lock = Any()

val threads = List(100) {
    thread {
        repeat(1000) {
            synchronized(lock) {
                counter++
            }
        }
    }
}

threads.forEach { it.join() }

println("Final counter value: $counter")
// Final counter value: 100000