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Because the check for integer overflow following the addition is absent, the caller must ensure that the increment() method is called no more than Integer.MAX_VALUE times for any key. Refer to INT00-J. Perform explicit range checking to ensure integer operations do not overflow for more information.

Compliant Solution (

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atomic method)

To ensure atomicity, this compliant solution uses a private final lock object to synchronize the statements of the increment() and getCount() methodsmethod that guarantees atomicity (AtomicInteger.incrementAndGet()). This provides a happens-before relationship between reading and writing any integer values in the map.

final class KeyedCounter {
  private final ConcurrentMap<String, AtomicInteger> map =
    new ConcurrentHashMap<String, AtomicInteger>();

  public void increment(String key) {
    AtomicInteger value = new AtomicInteger(0);
    AtomicInteger old = map.putIfAbsent(key, value);
   
    if (old != null) { 
      value = old; 
    }

    value.incrementAndGet(); // Increment the value atomically
  }

  public Integer getCount(String key) {
    AtomicInteger value = map.get(key);
    return value.get();
  }

  // Other accessors ...
}

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