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 order | Since 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 version | This 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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