What is the difference between Lists, ArrayLists, Maps, Hashmaps, Collections etc..?

Question

I\'ve been using HashMaps since I started programming again in Java without really understanding these Collections thing.

Honestly I am not really sure if using HashMaps

Answer 1

A Map vs a List.

In a Map, you have key/value pairs. To access a value you need to know the key. There is a relationship that exists between the key and the value that persists and is not arbitrary. They are related somehow. Example: A persons DNA is unique (the key) and a persons name (the value) or a persons SSN (the key) and a persons name (the value) there is a strong relationship.

In a List, all you have are values (a persons name), and to access it you need to know its position in the list (index) to access it. But there is no permanent relationship between the position of the value in the list and its index, it is arbitrary.