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public class CounterDemo1 {

    private final Map<String, Long> urlCounter = new ConcurrentHashMap<>();

    //接口调用次数+1

    public long increase(String url) {

        Long oldValue = urlCounter.get(url);

        Long newValue = (oldValue == null) ? 1L : oldValue + 1;

        urlCounter.put(url, newValue);

        return newValue;

    }

    //获取调用次数

    public Long getCount(String url){

        return urlCounter.get(url);

    }

    public static void main(String[] args) {

        ExecutorService executor = Executors.newFixedThreadPool(10);

        final CounterDemo1 counterDemo = new CounterDemo1();

        int callTime = 100000;

        final String url = "http://localhost:8080/hello";

        CountDownLatch countDownLatch = new CountDownLatch(callTime);

        //模拟并发情况下的接口调用统计

        for(int i=0;i<callTime;i++){

            executor.execute(new Runnable() {

                @Override

                public void run() {

                    counterDemo.increase(url);

                    countDownLatch.countDown();

                }

            });

        }

        try {

            countDownLatch.await();

        } catch (InterruptedException e) {

            e.printStackTrace();

        }

        executor.shutdown();

        //等待所有线程统计完成后输出调用次数

        System.out.println("调用次数："+counterDemo.getCount(url));

    }

}

console output：

调用次数：96526

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/**

 * Replaces the entry for a key only if currently mapped to a given value.

 * This is equivalent to

 *  <pre> {@code

 * if (map.containsKey(key) && Objects.equals(map.get(key), oldValue)) {

 *   map.put(key, newValue);

 *   return true;

 * } else

 *   return false;

 * }</pre>

 *

 * except that the action is performed atomically.

 */

boolean replace(K key, V oldValue, V newValue);

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public long increase2(String url) {

        Long oldValue, newValue;

        while (true) {

            oldValue = urlCounter.get(url);

            if (oldValue == null) {

                newValue = 1l;

                //初始化成功，退出循环

                if (urlCounter.putIfAbsent(url, 1l) == null)

                    break;

                //如果初始化失败，说明其他线程已经初始化过了

            } else {

                newValue = oldValue + 1;

                //+1成功，退出循环

                if (urlCounter.replace(url, oldValue, newValue))

                    break;

                //如果+1失败，说明其他线程已经修改过了旧值

            }

        }

        return newValue;

    }

console output：

调用次数：100000

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/**

     * If the specified key is not already associated

     * with a value, associate it with the given value.

     * This is equivalent to

     *  <pre> {@code

     * if (!map.containsKey(key))

     *   return map.put(key, value);

     * else

     *   return map.get(key);

     * }</pre>

     *

     * except that the action is performed atomically.

     *

     * @implNote This implementation intentionally re-abstracts the

     * inappropriate default provided in {@code Map}.

     *

     * @param key key with which the specified value is to be associated

     * @param value value to be associated with the specified key

     * @return the previous value associated with the specified key, or

     *         {@code null} if there was no mapping for the key.

     *         (A {@code null} return can also indicate that the map

     *         previously associated {@code null} with the key,

     *         if the implementation supports null values.)

     * @throws UnsupportedOperationException if the {@code put} operation

     *         is not supported by this map

     * @throws ClassCastException if the class of the specified key or value

     *         prevents it from being stored in this map

     * @throws NullPointerException if the specified key or value is null,

     *         and this map does not permit null keys or values

     * @throws IllegalArgumentException if some property of the specified key

     *         or value prevents it from being stored in this map

     */

     V putIfAbsent(K key, V value);

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private AtomicLongMap<String> urlCounter3 = AtomicLongMap.create();

public long increase3(String url) {

    long newValue = urlCounter3.incrementAndGet(url);

    return newValue;

}

public Long getCount3(String url) {

    return urlCounter3.get(url);

}