20 April 2019
Java ConcurrentHashMap
by Jerry Zhang
#Tip of the Day: 不积跬步，无以至千里；不积小流，无以成江海。
Why use ConcurrentHashMap?
HashMap: In multi-threads environment, HashMap is not secure. No protection, 100% forbidden!
HashTable: use synchronized to secure concurrency, but efficiency is poor. This is because it locks the whole table with only one key.
ConcurrentHashMap: divide the table into smaller segments, for each segment, use one lock to protect it.
