Summary

Hashing is the art (and science) of creating a single representation (typically a number) from an arbitrary object, be it strings, type instances, or collections; there is a way to break them down into a number that should reflect a particular use case. The real question is what you want to achieve and what characteristics are expected from the outcome. Cryptographic hashing deals with minimizing collisions and creating signatures that create a very different hash from minor modifications, whereas GeoHashes are a way to hierarchically structure Earth's coordinates into a string. Whenever two (or more) inputs to a hash function lead to the same output, this is called a collision—a bad sign for any cryptographic hashing, but fine if it's mostly about storing something in a hash map, as long as the collisions are evenly distributed. Most importantly, however, software engineers should never come up with their own hash functions, especially if security is a concern.

Maps store and manage...