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Java

Posted by Matthew Francis
Matthew Francis
6,967 Points

Newbie - What are hashcodes?

The treehouse video didnt really go into details in it, but after some research I'm guessing it is a number used to quickly distinguish/store/retrieve objects? Please correct me if I'm wrong!

Also, I also tried reading about hashMaps/hashSets, but I can't seem to comprehend what they are used for.

1 Answer

Seth Kroger
Seth Kroger
56,416 Points

Hashing is a large and complex topic in computer science but it basically means to reduce an arbitrary amount of data into a single number (or a fixed number of bits).

https://en.wikipedia.org/wiki/Hash_function

hashCode() gives you an integer which is computed from an object's contents (or memory address) which can be used to place the object in a hash table. One way to think of a hash table is a fixed set of numbered bins. The hash code is the bin number. (Or here the remainder hashCode() divided by the number of bins.) To retrieve an object, you just need search the object's single bin instead of all the objects in the table.

HashMap and HashSet are just implementations of Map and Set using a hash table to store their data.