Java 并发编程之 AtomicInteger AtomicLong

说明

AtomicInteger和AtomicLong原子类，保证了并发时线程安全的累加操作。底层是使用CAS原理。

AtomicInteger

原子整型类

AtomicInteger atomicInteger = new AtomicInteger();
// 获取当前的值
atomicInteger.get();
// 先获取当前的值，再加 1
atomicInteger.getAndIncrement();
// 先加1，再获取加 1 后的值
atomicInteger.incrementAndGet();
// 比较并交换
atomicInteger.compareAndSet(0, 2021);

AtomicLong

原子长整型类

AtomicLong atomicLong = new AtomicLong();
atomicLong.get();
atomicLong.getAndIncrement();
atomicLong.incrementAndGet();
atomicLong.compareAndSet(2, 2021);

小案例

public class AtomicLongDemo {

    public static void main(String[] args) throws InterruptedException {
        AtomicLong atomicLong = new AtomicLong();

        List<Thread> threads = new ArrayList<>();

        for (int i = 0; i < 10; i++) {
            Thread thread = new Thread(() -> {

                while (true) {
                    long prev = atomicLong.get();
                    long next = prev + 100;
                    boolean result = atomicLong.compareAndSet(prev, next);
                    if (result) {
                        System.out.println("success thread#" + Thread.currentThread().getName() + ", prev#" + prev + ", next#" + next);
                        break;
                    } else {
                        System.out.println("fail thread#" + Thread.currentThread().getName() + ", prev#" + prev + ", next#" + next);
                    }
                }

            }, "t" + i);
            threads.add(thread);
        }
        threads.forEach(Thread::start);
        for (Thread thread : threads) {
            thread.join();
        }
        System.out.println(atomicLong.get());
    }

}

输出：

success thread#t5, prev#300, next#400
success thread#t4, prev#600, next#700
success thread#t0, prev#0, next#100
success thread#t6, prev#200, next#300
fail thread#t7, prev#100, next#200
success thread#t3, prev#400, next#500
success thread#t2, prev#500, next#600
success thread#t9, prev#100, next#200
success thread#t1, prev#700, next#800
fail thread#t8, prev#600, next#700
success thread#t8, prev#900, next#1000
success thread#t7, prev#800, next#900
1000