![]() ![]() Int index = hash & (n - 1) //n is the capacity or size of HashMap. ![]() Int hash = hash(k) //calculates the hashcode e.g. The modulus operation ensures the index to be in the range 0.size of hashmap -1. Now, to add this key-value pair in a Map, first, the hashcode of the key is generated and a bit-wise modulus operation(&) is performed with the size of HashMap(15) to find the exact bucket number. Put() operation accepts K as a key and V as a. We mainly perform 2 operations in a HashMap - put() and get(). ![]() A custom implementation of LinkedList can be found here. Meaning, HashMap internally uses LinkedList to store the key-value pair. This entry object has the key, value, hashcode of the key and a pointer to the next node. The bucket is nothing but an Array of an Entry object. Map map = new HashMap(5) Ībove statement creates an instance of HashMap with a default bucket size of 16(0.15). A good explanation can be found here on Youtube by Ranjith.Īn instance of HashMap can be created with a new operator. Let us discuss how HashMap works internally in brief. If the key is null then that element will be stored in a zero location in Entry array. It does not allow any duplicate key and allows only one null key. It internally uses the Hashing technique to find the exact bucket number and hence can provide constant-time performance for the basic operations such as to get and put. HashMap is an implementation of the Map interface that provides storage for key-value pairs. First, we will discuss how the HashMap provided in Java API actually works internally in brief so that it will be easier with its custom implementation and then we will implement different CRUD operations such as put(), get(), delete() on the HashMap and it's best and worst-case complexity. In this article, we will be creating a custom HashMap implementation in Java. ![]()
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