The following article describes What is the Difference Between HashMap and HashTable Classes in Java.
In fact, both HashMap and Hashtable are the classes available in Java that implement the Map interface. These classes allow you to store key-value pairs. However, they have some key differences in terms of their internal implementation, methods, and thread safety.
Meanwhile, the main difference between HashMap and Hashtable is that HashMap is not synchronized. In other words, multiple threads can access it simultaneously. Therefore, it can lead to data inconsistencies if multiple threads modify the map concurrently. On the other hand, Hashtable is synchronized. So, it makes it thread-safe. However, this synchronization comes at a performance cost. So, accessing Hashtable is slower than accessing HashMap.
Another difference between HashMap and Hashtable is that HashMap allows null values and null keys. Whereas Hashtable does not allow null values or keys.
Finally, some of the methods in Hashtable have been deprecated in favor of the equivalent methods in HashMap. For example, the put method in Hashtable has been replaced by the put method in HashMap.
Summary – Difference Between HashMap and HashTable
To summarize, if you need a fast, unsynchronized map, use HashMap. In contrast, if you need a thread-safe map, use Hashtable. However, if performance is a concern, consider using other thread-safe collections, such as ConcurrentHashMap, which provide better concurrency performance than Hashtable.
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