In this section, you will learn about the HashTable class, also known as HashMap, a hash implementation of the Dictionary class.

Hashing consists of finding a value in a data structure in the shortest time possible. You have learned from previous chapters that if we would like to get a value from it (using a get method), we need to iterate through the structure until we find it. When we use a hash function, we already know which position the value is in, so we can simply retrieve it. A hash function is a function that given a key, and will return an address in the table where the value is.

For example, let's continue using the e-mail address book we used in the previous section. The hash function we will use is the most common one, called a "lose lose" hash function, where we simply sum up the ASCII values of each character of the key length.