.

Then, how do you rehash a hash table?

Rehashing of a hash map is done when the number of elements in the map reaches the maximum threshold value. When rehashing occurs a new hash function or even the same hash function could be used but the buckets at which the values are present could change.

Likewise, why do you need a hash table? They are widely used in many kinds of computer software, particularly for associative arrays, database indexing, caches and sets. The idea of a hash table is to provide a direct access to its items. So that is why the it calculates the "hash code" of the key and uses it to store the item, insted of the key itself.

Also to know, what is a hash table data structure?

Hash Table is a data structure which stores data in an associative manner. In a hash table, data is stored in an array format, where each data value has its own unique index value. Thus, it becomes a data structure in which insertion and search operations are very fast irrespective of the size of the data.

Why are hash tables fast?

A common mistake is to use cryptographic hash functions when security is not needed, cryptographic hash functions are slower than regular hash functions and for lookups there's no need for a cryptographic hash function. So a hash table is fast if and because the hashing function is fast.