How is safe usage of HashMap implemented in multithreading conditions?

To safely use HashMap in a multithreaded environment, several approaches can be applied:

1. Use Collections.synchronizedMap(new HashMap<>()) — returns a synchronized wrapper around HashMap, where all methods are blocked to ensure thread safety.

2. Use ConcurrentHashMap — a specialized Map implementation optimized for concurrent access without full locking.

3. Manually synchronize access to HashMap using the synchronized keyword or other synchronization mechanisms.

Example of using ConcurrentHashMap:

import java.util.concurrent.ConcurrentHashMap;

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

This class provides high performance when multiple threads access it simultaneously without the risk of race conditions.