ConcurrentHashMap Examples

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We can provide you with a brief explanation and code snippets for 20 different scenarios where `ConcurrentHashMap` in Java can be used.

1. Basic Usage of ConcurrentHashMap:

   Ensure thread-safe operations with concurrent reads and writes.

ConcurrentHashMap<String, Integer> map = new ConcurrentHashMap<>();
map.put("One", 1);
map.get("One");

2. Atomic Updates in ConcurrentHashMap:

   Perform atomic updates without the need for external synchronization.

map.compute("One", (key, value) -> value + 1);

3. Bulk Operations in ConcurrentHashMap:

   Use `forEach` for parallel processing of entries.

map.forEach((key, value) -> processEntry(key, value));

4. Conditional Removal in ConcurrentHashMap:

   Remove an entry only if a certain condition is met.

map.remove("One", 1);

5. Default Values in ConcurrentHashMap:

   Provide default values for non-existing keys.

map.computeIfAbsent("Two", key -> 2);

6. Merge Function in ConcurrentHashMap:

   Merge values for a key using a custom merging function.

map.merge("One", 10, Integer::sum);

7. Search and Update in ConcurrentHashMap:

   Search for a key and update its value atomically.

map.search("One", (key, value) -> {
        if (value > 5) {
        map.replace(key, value, value * 2);
        }
        return value;
        });

8. Grouping By in ConcurrentHashMap:

   Group elements by a specific property.

Map<Boolean, List<String>> groupedByLength = map.keySet()
        .stream()
        .collect(Collectors.groupingBy(key -> key.length() > 3));

9. Parallel Processing in ConcurrentHashMap:

   Parallelize processing with `forEachParallel` for improved performance.

map.forEachEntryParallel(2, entry -> processEntry(entry.getKey(), entry.getValue()));

10. Key Set Operations in ConcurrentHashMap:

    Perform atomic operations on the key set.

map.keySet().removeIf(key -> key.length() > 3);

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11. Conditional Addition in ConcurrentHashMap:

    Add a key-value pair only if the key is absent.

map.putIfAbsent("Three", 3);

12. Concurrent Reduction in ConcurrentHashMap:

    Use `reduceEntries` for concurrent reduction.

int sum = map.reduceEntries(2, (entry) -> entry.getValue(), Integer::sum);

13. Iterating Values in ConcurrentHashMap:

    Iterate over values using `forEachValue`.

map.forEachValue(2, value -> processValue(value));

14. Updating Values in ConcurrentHashMap:

    Update values conditionally.

map.replaceAll((key, value) -> value > 5 ? value * 2 : value);

15. Key Filtering in ConcurrentHashMap:

    Filter keys based on a predicate.

Set<String> filteredKeys = map.keySet().stream()
        .filter(key -> key.startsWith("O"))
        .collect(Collectors.toSet());

16. Concurrent Enumeration in ConcurrentHashMap:

    Enumerate over entries while allowing concurrent modifications.

Enumeration<String> keys = map.keys();
        while (keys.hasMoreElements()) {
        String key = keys.nextElement();
        // process key
        }

17. Concurrent Search in ConcurrentHashMap:

    Use `searchEntries` for concurrent search operations.

String result = map.searchEntries(2, entry -> entry.getValue() > 5 ? entry.getKey() : null);

18. Customized Equality in ConcurrentHashMap:

    Use a custom `Object` as a key with overridden `equals` and `hashCode`.

class CustomKey {
    // Override equals and hashCode
}
ConcurrentHashMap<CustomKey, String> customMap = new ConcurrentHashMap<>();

19. Thread-safe Initialization in ConcurrentHashMap:

    Ensure thread-safe lazy initialization.

map.computeIfAbsent("LazyInit", key -> initializeValue());

20. Concurrent Replace in ConcurrentHashMap:

    Replace an existing value for a key atomically.

map.replace("One", 1, 10);

These examples showcase the versatility of `ConcurrentHashMap` in various scenarios, from basic usage to advanced concurrent operations.

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