ConcurrentHashMap forEach and reduce reads in parallel

The bulk operations take a parallelism threshold and can traverse concurrently, which suits large read-mostly maps.

Code

var map = new ConcurrentHashMap<String, Integer>();
for (int i = 1; i <= 100; i++) map.put("k" + i, i);

long sum = map.reduceValues(1, Integer::longValue, Long::sum);
System.out.println("sum of 1..100 = " + sum);

Integer found = map.search(1, (k, v) -> v == 42 ? v : null);
System.out.println("search found = " + found);
System.out.println("mappingCount = " + map.mappingCount());

Output

sum of 1..100 = 5050
search found = 42
mappingCount = 100

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Published 2026-07-30