AtomicInteger 的实际用途 [英] Practical uses for AtomicInteger

问题描述

我有点理解 AtomicInteger 和其他 Atomic 变量允许并发访问.在什么情况下通常使用这个类?

I sort of understand that AtomicInteger and other Atomic variables allow concurrent accesses. In what cases is this class typically used though?

推荐答案

AtomicInteger 主要有两个用途:

• 作为一个原子计数器(incrementAndGet()等)，可以被多个线程同时使用

• As an atomic counter (incrementAndGet(), etc) that can be used by many threads concurrently

作为支持 compare-and-swap 指令的原语(compareAndSet()) 来实现非阻塞算法.

As a primitive that supports compare-and-swap instruction (compareAndSet()) to implement non-blocking algorithms.

以下是来自 的非阻塞随机数生成器示例Brian Göetz 的 Java 并发实践:

public class AtomicPseudoRandom extends PseudoRandom {
    private AtomicInteger seed;
    AtomicPseudoRandom(int seed) {
        this.seed = new AtomicInteger(seed);
    }

    public int nextInt(int n) {
        while (true) {
            int s = seed.get();
            int nextSeed = calculateNext(s);
            if (seed.compareAndSet(s, nextSeed)) {
                int remainder = s % n;
                return remainder > 0 ? remainder : remainder + n;
            }
        }
    }
    ...
}

如您所见，它的工作方式与 incrementAndGet() 基本相同，但执行任意计算(calculateNext())而不是增量(并处理返回前的结果).

As you can see, it basically works almost the same way as incrementAndGet(), but performs arbitrary calculation (calculateNext()) instead of increment (and processes the result before return).

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