Does HashMap ensure safe operation when used in a multithreaded environment?

HashMap in Java is not thread-safe. This means that when accessed concurrently from multiple threads without external synchronization, issues such as data corruption or incorrect behavior may occur.

If you need to use a map in a multithreaded environment, you can:

• Use Collections.synchronizedMap(new HashMap<>()) to obtain a synchronized version.
• Use the ConcurrentHashMap class, which is specifically designed for concurrent access and provides better performance.

Example of using ConcurrentHashMap:

import java.util.concurrent.ConcurrentHashMap;

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

Thus, for safe operation in a multithreaded environment, it is better to use ConcurrentHashMap or manually synchronize access to HashMap.