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

■ List — An ordered collection of elements that allows duplicate entries

Concrete Classes:

ArrayList — Standard resizable list.
LinkedList — Can easily add/remove from beginning or end.
Vector — Older thread-safe version of ArrayList.
Stack — Older last-in, first-out class.

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■ Set — Does not allow duplicates

Concrete Classes:

HashSet—Uses hashcode() to find unordered elements.
TreeSet—Sorted and navigable. Does not allow null values.

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■ Queue — Orders elements for processing

Concrete Classes:

LinkedList — Can easily add/remove from beginning or end.
ArrayDeque—First-in, first-out or last-in, first-out. Does not allow null values.

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■ Map — Maps unique keys to values

Concrete Classes:

HashMap — Uses hashcode() to find keys.
TreeMap — Sorted map. Does not allow null keys.
Hashtable — Older version of hashmap. Does not allow null keys or values.