Difference: HashMap vs HashTable

HashMap and HashTable differ based on the following parameters:

• Nature

           HashMap is not synchronized in nature.

           HashTable is synchronized in nature

• Traversed by

           HashMap can be traversed by using an iterator

           HashTable can be traversed by using an iterator or enumerator

• Null value/key

          HashMap allows only one null key and any number of null values.

          HashTable doesn't allow key or value as null.

• fail-fast nature of iterator

          Iterator in HashMap is fail-fast.

          Enumerator in HashTable is not fail-fast.

• Performance

          HashMap is faster performance wise.

          HashTable is slower in comparision to HashMap performance wise.

          

          Reason: Since HashTable is synchronized in nature so it doesn't allow multi-threading                                       operation on a particular resource at a time thus turning out to be slower than                                       HashMap which is non-synchronized by nature.

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• ArrayList vs LinkedList
• ArrayList vs Vector
• Collection vs Collections
• ArrayList vs HashSet
• Iterator vs Enumeration