Synchronized Collections vs Concurrent Collections

In this post, we will learn the difference between Synchronized Collections and Concurrent Collections in Java. This is a frequently asked question in Java interviews for beginners. Let's dive into it.

Difference between Synchronized Collections and Concurrent Collections in Java

Feature Synchronized Collections Concurrent Collections
Thread Safety Thread-safe using locks Thread-safe using non-blocking algorithms or fine-grained locking mechanisms
Locking Mechanism Locks the entire collection Utilizes non-blocking algorithms or fine-grained locks to allow concurrent access
Performance May suffer from contention and performance issues in high-concurrency scenarios Designed for high-concurrency scenarios with better performance in multi-threaded environments
Collection Types Synchronized versions of standard collections (e.g., Collections.synchronizedList, Collections.synchronizedMap) A separate set of classes in java.util.concurrent package (e.g., ConcurrentHashMap, ConcurrentSkipListMap)
Blocking Operations Blocking operations when modifying the collection Non-blocking operations for read and some write operations, providing better concurrency
Iterators May throw ConcurrentModificationException during iteration if the collection is modified Designed to handle concurrent modifications gracefully and not throw ConcurrentModificationException