Comment by redcalx

You do hash % bucketCount to find your bucket/slot. Each array element is also a linked list node (with a next pointer), thus if the slot is populated you follow the linked list until an empty slot is found and attach to the end of the linked list.

I figure it works best if you over allocate slots, so that on average you only have to do very few hops on each linked list walk (or no walk at all).

Aside: This is the method employed by .NET's Dictionary<K,V> class.

Further - it's generally faster to use structure of arrays rather than array of structures, thus in the above scheme the dictionary items/payloads and the linked list pointers could be in separate arrays.