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Differences between HashMap and TreeMap

Differences between HashMap and TreeMap

HashMap and TreeMap are both types of map implementation in Java. While they share some common properties, there are also some important differences. In this blog post, we’ll explore those differences and discuss when you might want to use one over the other.

What is HashMap?

  • HashMap is a data structure that HashMap HashMap stores key-value pairs. HashMap HashMap HashMap HashMap HashMap HashMap HashMap HashMap HashMap HashMap Hashmap is a data structure that stores key-value pairs.
  • It is similar to the Array, but the only difference is that in an Array, the key needs to be an integer whereas in HashMap it can be any object. A HashMap Hashmap consists of two parts: an array called buckets and a Linked List.
  • In the background, there is a hashing function that will take the key and generate an index where the value will be stored. Whenever we want to retrieve a value, we need to provide the key, and the hashing function will help us fetch the required value from the Linked List. The main advantage of using a Hashmap is that it provides constant time complexity for basic operations like put, get, and containsKey. However, one drawback is that it doesn’t maintain any order.

What is TreeMap?

TreeMap is a data structure that allows you to store data in a tree-like structure. The TreeMap class is part of java. util package and it provides a way to store data in a sorted, hierarchical fashion. TreeMap is similar to the TreeSet class, but it allows you to store data in key/value pairs, rather than just keys. TreeMap is an implementation of the SortedMap interface, which means it provides a way to sort your data using either natural ordering or a custom comparator. TreeMap also implements the NavigableMap interface, which provides several methods for traversing your data in different ways. You can use TreeMap to store data in any number of ways, but it’s particularly well-suited for storing data that needs to be sorted or searched.

Differences between HashMap and TreeMap

  • HashMap and TreeMap are two of the most commonly used data structures in Java. Both are used to store key-value pairs, but they differ in how the keys are stored and retrieved. HashMap uses a hashing algorithm to store keys, which means that keys are not stored in any particular order.
  • This makes HashMap more efficient for retrieving values, but it also means that HashMap does not support ordering operations such as sorting. TreeMap, on the other hand, uses a balanced tree data structure to store keys.
  • This allows TreeMap to support ordering operations, but it also makes retrieval slightly less efficient. In general, HashMap is a better choice when performance is the primary concern, while TreeMap is a better choice when ordering is necessary.


The two Java map implementations, HashMap and TreeMap, offer different functionality. In general, HashMaps are better for applications that need quick lookup times, while TreeMaps perform better when you need to traverse the tree structure. If you’re not sure which type of map is best for your application, try testing both and see which performs better.

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