There are a good number of articles that articulate functional differences between HashMap, HashTable and ConcurrentHashMap. This post compares the performance behavior of these data structures through practical examples. If you don’t have patience to read the entire post, here is bottom line: When you confront with the decision of whether to use HashMap or HashTable or ConcurrentHashMap, you can consider using ConcurrentHashMap since it’s thread-safe implementation, without compromise in performance.