Difference Between Hashtable And HashMap

Hashtable :

• Hashtable is thread-safe i.e. its methods are synchronized.
• Hashtable does not allow null keys or null values.
• Use Hashtable , when you need to have synchronization.

HashMap :

• HashMap is not thread-safe or non-synchronized.
• Performance-wise HashMap is more suitable as it does not have overheads of  threads.
• HashMap allows one null key and any number of null values.