Do you have experience working with collections implemented for safe multithreading?

In Java, to work safely with collections in a multithreaded environment, special classes from the java.util.concurrent package and wrapper methods from Collections are used. For example, ConcurrentHashMap is a thread-safe version of HashMap that allows multiple threads to read and write without locking the entire collection. There is also CopyOnWriteArrayList — a thread-safe list that copies the internal array upon modifications, which is convenient for scenarios with frequent reads and infrequent writes.

For wrappers, you can use Collections.synchronizedList(new ArrayList<>()), which synchronizes access to the list but requires external synchronization during iteration.

Example of using ConcurrentHashMap:

import java.util.concurrent.ConcurrentHashMap;

ConcurrentHashMap<String, Integer> map = new ConcurrentHashMap<>();
map.put("key1", 1);
map.put("key2", 2);

// Safe for multiple threads
int value = map.get("key1");

Thus, for multithreaded work, collections from java.util.concurrent or synchronized wrappers are chosen, depending on performance requirements and the nature of operations.