iDev: True difference between Hash Table and Dictionary

True difference between Hash Table and Dictionary

S.No.

Dictionary

Hash Table

1

A dictionary is a data structure that maps keys to values.

A hash table is a data structure that maps keys to values by taking the hash value of the key (by applying some hash function to it) and mapping that to a bucket where one or more values is stored.

2

Dictionary is not a threadsafe.

Hashtable is threadsafe.

3

Dictionary is types means that the values need not to boxing.

Hashtable values need to be boxed or unboxed because it stored the values and keys as objects.        

4

When you try to get the value of key which does not exists in the collection, the dictionary throws an exception of ‘KeyNotFoundException’.

When you try to get the value of key which does not exists in the collection, the Hashtable returns a NULL value.

5

When using large collection of key value pairs dictionary is not as good as Hashtable.

When using large collection of key value pairs hashtable would be considered more efficient than dictionary.

6

When we retrieve the record in collection the dictionary maintains the order of entries by which entries were added.

When we retrieve the record in collection the hashtable does not maintain the order of entries.

7

Dictionary relies on chaining.

Hashtable relies on rehashing.

8

Dictionary is Abstract Base class of Hash Table.

Hash Table is Derived by Dictionary class.

9

Dictionary is Generic Type.

Hash Table is not generic type.

 

Advertisements

Leave a Reply

Please log in using one of these methods to post your comment:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s