Hash Table Load Factor and Capacity
This is an excerpt from the more extensive article on Hash Tables.
The load factor is the average number of key-value pairs per bucket.
It is when the load factor reaches a given limit that rehashing kicks in. Since rehashing increases the number of buckets, it reduces the load factor.
The load factor limit is usually configurable and offers a tradeoff between time and space costs.
The default load factor for a Java
HashMap is 0.75 and for a C#
Hashtable it’s 1.0.
The capacity is the maximum number of key-value pairs for the given load factor limit and current bucket count.
Since rehashing increases the number of buckets, it increases the capacity.
The default initial capacity for a Java
HashMap is 12 and for a C#
Hashtable it’s 0, i.e. the bucket array is initialized lazily upon first insertion.
Here’s the structure of a hash table, configured with load factor limit of 4.