What are the differences between a HashMap and a Hashtable in Java?
There are several differences between a HashMap and a
Hashtable in Java:
Hashtableis synchronized, while HashMap is not. This means that
Hashtableis thread-safe, while HashMap is not. If you need a thread-safe map, you should use
Hashtableor one of the other concurrent maps provided by the
Null keys and values:
Hashtabledoes not allow null keys or values, while HashMap allows one null key and any number of null values.
Hashtableis generally slower than HashMap due to its synchronization. If you don't need the thread-safety provided by
Hashtable, you should use HashMap for better performance.
Hashtableiterates over the elements in the order they were added, while HashMap does not make any guarantees about the iteration order. The order of the elements in a HashMap may change if the map is modified.
Hashtablehas a number of legacy methods that are not present in HashMap, such as
elements(). These methods have been replaced by newer methods in HashMap, such as
Hashtablewas introduced in Java 1.0, and does not use type parameters. To use a
Hashtablewith a specific key and value type, you need to use type casting. In contrast, HashMap was introduced