Difference Between HashMap vs LinkedHashMap In Java Detail

HashMap vs LinkedHashMap In Java: In this article, we will discuss the difference between HashMap and LinkedHashMap classes in detail i.e.; HashMap vs LinkedHashMap

Lets us move on and discuss the key differences between these 2 Map implemented classes

HashMap vs LinkedHashMap

HashMap LinkedHashMap
Uses a hash table to store map entries (i.e.; key-value pairs)Uses a combination of hash table + LinkedList to store map entries (i.e.; key-value pairs)
Doesn’t maintain insertion order i.e.; while iterating through HashMap, we will get map entries in random orderSince it uses the doubly-linked list to store map entries (i.e.; key-value pairs), maintains insertion order
This is introduced in the original collection framework in Java 1.2 versionThis is introduced in Java 1.4 version

When to use HashMap?

  • HashMap stores key-value pairs which use a hashing technique to store key-value pairs
  • So, the search operation is faster
  • So, if the business requirement is to store key-value pairs for faster search operation or number of search operation on the basis of keys; without concerning insertion order
  • Then, HashMap is the very apt choice

When to use LinkedHashMap?

  • This is exactly the same as that of HashMap, but underlying data structure to hold key-value pairs is different
  • It uses a doubly-linked list which allows holding key-value pairs as per insertion order
  • So, if a business requirement is to store key-value pairs for faster search operation or number of search operation concerning/maintaining insertion order
  • Then, LinkedHashSet is the very apt choice which maintains insertion order
  • So while iterating through LinkedHashSet, we will get map entry (key-value pairs) as per insertion order (as against random in HashMap)

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