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

The API is pretty clear about the differences and/or relations between them:

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Collection

The root interface in the collection hierarchy. A collection represents a group of objects, known as its elements. Some collections allow duplicate elements and others do not. Some are ordered and others unordered.

http://download.oracle.com/javase/6/docs/api/java/util/Collection.html

List

An ordered collection (also known as a sequence). The user of this interface has precise control over where in the list each element is inserted. The user can access elements by their integer index (position in the list), and search for elements in the list.

http://download.oracle.com/javase/6/docs/api/java/util/List.html

Set

A collection that contains no duplicate elements. More formally, sets contain no pair of elements e1 and e2 such that e1.equals(e2), and at most one null element. As implied by its name, this interface models the mathematical set abstraction.

http://download.oracle.com/javase/6/docs/api/java/util/Set.html

Map

An object that maps keys to values. A map cannot contain duplicate keys; each key can map to at most one value.

http://download.oracle.com/javase/6/docs/api/java/util/Map.html

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Is there anything in particular you find confusing about the above? If so, please edit your original question. Thanks.