Java ConcurrentHashMap is better than HashMap performance wise?

Question

I was just reading the book Clean Code and came across this statement:

When Java was young Doug Lea wrote the seminal book[8] Concurrent Programming

Answer 1

If you are accessing the HashMap with only a single thread HashMap is fastest (it does not do any synchronization), if you are accessing it from multiple threads ConcurrentHashMap is faster than doing the synchronization coarse-grained by hand. See here for a little comparison:

http://www.codercorp.com/blog/java/why-concurrenthashmap-is-better-than-hashtable-and-just-as-good-hashmap.html