Java并发中的原子类详细代码实例

public class Counter {
    private int count = 0;

    public void increment() {
        count++;
    }
}

public synchronized void increment() {
    count++;
}

private AtomicInteger count = new AtomicInteger(0);

public void increment() {
    count.incrementAndGet();
}

AtomicInteger count = new AtomicInteger(0);

// 加1
count.incrementAndGet();  // ++i
count.getAndIncrement();  // i++

// 减1
count.decrementAndGet();  // --i
count.getAndDecrement();  // i--

// 加任意值
count.addAndGet(5);

// 获取值
int value = count.get();

// 设置值
count.set(100);

// CAS 操作
count.compareAndSet(100, 200);  // 如果当前值是100，则设置为200

AtomicLong count = new AtomicLong(0);
count.incrementAndGet();

AtomicBoolean flag = new AtomicBoolean(false);

// 设为 true
flag.set(true);

// CAS 操作
flag.compareAndSet(false, true);

AtomicReference<User> userRef = new AtomicReference<>();

User user1 = new User("张三", 20);
User user2 = new User("李四", 25);

userRef.set(user1);
userRef.compareAndSet(user1, user2);  // 如果当前是 user1，则改为 user2

// 数组中某个元素原子操作
AtomicIntegerArray arr = new AtomicIntegerArray(new int[]{1, 2, 3});

arr.getAndAdd(0, 10);  // 第一个元素加10
int value = arr.get(0);  // 获取第一个元素

LongAdder count = new LongAdder();

count.add(1);
count.increment();
long value = count.sum();

// AtomicInteger vs LongAdder
// 低并发：两者差不多
// 高并发：LongAdder 性能更好

public class PageViewCounter {
    private AtomicInteger count = new AtomicInteger(0);

    public void addView() {
        count.incrementAndGet();
    }

    public int getViews() {
        return count.get();
    }
}

public class SubmitService {
    private AtomicBoolean submitting = new AtomicBoolean(false);

    public void submit() {
        // 如果已经在提交中，直接返回
        if (!submitting.compareAndSet(false, true)) {
            return;
        }

        try {
            // 业务逻辑
            doSubmit();
        } finally {
            submitting.set(false);
        }
    }
}

public class ConfigHolder {
    private AtomicReference<Config> configRef = new AtomicReference<>();

    public void updateConfig(Config newConfig) {
        configRef.updateAndGet(old -> newConfig);
    }

    public Config getConfig() {
        return configRef.get();
    }
}