var counter = 0L
fun increment() {
    // 這個(gè)操作在并發(fā)場(chǎng)景下會(huì)出錯(cuò)！
    counter++ 
}

// 偽代碼實(shí)現(xiàn)
fun incrementAndGet(): Long {
    while(true) {
        val current = get()
        val next = current + 1
        if (compareAndSet(current, next)) {
            return next
        }
    }
}

// JDK源碼片段
private volatile long value;
public final long get() {
    return value;
}

// 初始值為0
val atomicCounter = AtomicLong()
// 帶初始值
val pageViewCounter = AtomicLong(1000)

class PageVisitTracker {
    private val visitCount = AtomicLong(0)
    // 注意：這個(gè)方法要在后臺(tái)線程調(diào)用
    fun trackVisit() {
        visitCount.incrementAndGet()
        if (visitCount.get() % 100 == 0L) {
            uploadToServer() // 每100次上報(bào)服務(wù)器
        }
    }
    fun getVisitCount() = visitCount.get()
}

class DownloadManager {
    private val progress = AtomicLong(0)
    fun updateProgress(bytes: Long) {
        progress.addAndGet(bytes)
        val current = progress.get()
        if (current % (1024 * 1024) == 0L) { // 每MB更新UI
            runOnUiThread { updateProgressBar(current) }
        }
    }
}

when {
    writeQPS < 1000 -> AtomicLong()
    writeQPS > 5000 -> LongAdder()
    else -> 根據(jù)業(yè)務(wù)精度要求選擇
}

if (atomicValue.get() > 100) {
    atomicValue.set(0) // 這兩個(gè)操作不是原子的！
}

while (true) {
    val current = atomicValue.get()
    if (current <= 100) break
    if (atomicValue.compareAndSet(current, 0)) break
}

val MAX = Long.MAX_VALUE
val counter = AtomicLong(MAX - 10)
repeat(20) {
    counter.incrementAndGet() // 最后會(huì)變成Long.MIN_VALUE
}

fun AtomicLong.update(action: (Long) -> Long) {
    while (true) {
        val current = get()
        val newValue = action(current)
        if (compareAndSet(current, newValue)) return
    }
}
// 使用示例
atomicCounter.update { it * 2 }

class MonitoredAtomicLong(
    initialValue: Long
) : AtomicLong(initialValue) {
    private val casFailureCount = AtomicInteger()
    override fun compareAndSet(expect: Long, update: Long): Boolean {
        val success = super.compareAndSet(expect, update)
        if (!success) casFailureCount.incrementAndGet()
        return success
    }
    fun printStats() {
        Log.d("AtomicStats", "CAS失敗次數(shù)：${casFailureCount.get()}")
    }
}