LinkedHashMap Tutorial

java.util.LinkedHashMap stores Key Value pairs like java.util.HashMap, and enables the retrieval of a Value given a Key.  LinkedHashMap differs from HashMap in that the Keys are ordered by their insertion order. LinkedHashMap maintains a double-linked list to determine insertion order.

This tutorial, complete with an easy to understand and interactive UML visualization, explains how LinkedHashMap works.

This is the fifth part in our java.util.Map series. Read the following prerequisite post first, before continuing with this post:

• Hashmap Introduction Tutorial
• Hashmap and the Importance of HashCode

Step through LinkedHashMap in action

Step through the visualisation from the above image, and read the yellow comments and the associated code.

When the code is executed, the following is output. Note how the results are in the same order as they were inserted.

Last Name     First Name    Rating
---------------------------------
Smith         Bill          5
Smith         Jack          4
Jackson       Bill          2
Smith         Andrew        1


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