CODEWITHSUNDEEP
javacollections
klijo
klijo

Reputation: 16461

java collections vs map in collections framework

According to http://docs.oracle.com/javase/tutorial/collections/interfaces/index.html there are two top level interfaces called collection and map.

Whats the exact reason for separating these two ?

Is it that all key value data structures implement the map interface and all others implement the collections interface ?

Upvotes: 8

Views: 8950

Answers (2)

TeaCupApp
TeaCupApp

Reputation: 11452

Yes, That's correct! Check all the List classes and then check all the Map related classes.

and there is this awesome discussion, ob this question

List vs Map in Java

Visually

This is a collection, by this you know that the books are there and it's in order like 0,1,2,3...

enter image description here

But in a Map, the books are in memory unordered but for the computer's convenience it has a key to find the books, like in a library.

enter image description here

Upvotes: 25

Jon Egeland
Jon Egeland

Reputation: 12623

A Map is a structure that has unique keys mapping to values. A Collection is just a grouping of multiple values with no specific key.

You can do the same comparison between a List and a Map to see the differences. This SO question deals with these differences.

Upvotes: 6

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