HashMap vs HashTable | Java

HashMap and Hashtable both are used to store data in key and value form. Both are using hashing technique to store unique keys. Differences between HashMap and Hashtable:

1. Hashtable is synchronized, whereas HashMap is not. This makes HashMap better for non-threaded applications, as unsynchronized Objects typically perform better than synchronized ones.
2. Hashtable does not allow null keys or values. HashMap allows one null key and any number of null values.
3. Hashtable is much slower than HashMap if used in Single threaded environment. So if you don’t need synchronization and HashMap is only used by one thread, it out perform Hashtable in Java.
4. Iterator in the HashMap is a fail-fast iterator while the enumerator for the Hashtable is not and throw ConcurrentModificationException if any other Thread modifies the map structurally by adding or removing any element except Iterator’s own remove() method.

Difference between Hashmap and Hashtable

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Difference between HashMap and Hashtable