In which memory area is ConcurrentHashMap stored? Which container should be used for storing metrics?

ConcurrentHashMap in Java is stored in the heap, like most objects in Java. It is a thread-safe implementation of Map, optimized for concurrent access.

For storing metrics, specialized containers are often used, such as structures from monitoring libraries like Micrometer or Dropwizard Metrics. Regarding general containers, suitable options for metrics include:

• ConcurrentHashMap — for storing counters and histograms with thread-safe access.
• AtomicLong, AtomicInteger — for atomic counters.

Example of using ConcurrentHashMap for metrics:

ConcurrentHashMap<String, AtomicLong> metrics = new ConcurrentHashMap<>();

// Incrementing a counter
metrics.computeIfAbsent("requests", k -> new AtomicLong()).incrementAndGet();