Commonly used data structures in Java

List

List is an ordered sequence of objects. Elements can be inserted or accessed at a specific index. Popular implementations – ArrayList, LinkedList,

Set

Set is a collection which doesn’t allow duplicates. Popular implementations – HashSet, LinkedHashSet, etc.

Map

Map supports dictionary format (key, value). Popular implementations – HashMap, TreeMap, etc.

Bag

Bag counts the number of times an element appears in the collection.  Popular implementation – Apache commons collection Bag interface.

BidiMap

It’s bi-directional map. Allows lookup based on key or value. Popular implementation – Apache commons collection BidiMap. Google Guava implementation of BidiMap.

Trie

It’s a prefix tree. Read more on trie. Popular implementation  Apache commons collection Trie.

Multi-Map

Map of Map. Apache commons collections and Google Guava provide multi-map implementations.

Table

A collection that attaches row key and column key to a value is called Table. Google Guava provides an Table implementations.

Graph

Data structure for graph representing nodes and connections between them. Google guava provides Graph implementation.