What is ConcurrentHashMap and Hashtable? In java, why is ConcurrentHashMap considered faster than Hashtable?

What is ConcurrentHashMap and Hashtable? In java, why is ConcurrentHas

1.	What is ConcurrentHashMap and Hashtable? In java, why is ConcurrentHashMap considered faster than Hashtable?
Answer» ConcurrentHashMap: It was introduced in Java 1.5 to store data using multiple buckets. As the name SUGGESTS, it allows CONCURRENT READ and writes operations to the map. It only locks a certain portion of the map while doing iteration to provide thread safety so that other readers can still have access to the map WITHOUT waiting for iteration to complete. Hashtable: It is a thread-safe legacy class that was introduced in old versions of java to store key or value pairs using a hash table. It does not provide any lock-free read, unlike ConcurrentHashMap. It just locks the entire map while doing iteration. ConcurrentHashMap and Hashtable, both are thread-safe but ConcurrentHashMap generally avoids read locks and improves performance, unlike Hashtable. ConcurrentHashMap also provides lock-free reads, unlike Hashtable. THEREFORE, ConcurrentHashMap is considered faster than Hashtable especially when the number of readers is more as compared to the number of writers.