Understanding the Difference Between Map and HashMap in Java

Difference Between Map and HashMap in Java

Java provides many powerful collection classes like Map and HashMap, however, they can be confusing for beginners due to their similarities. In this article, we will discuss the major differences between Map and HashMap classes in Java.

What is the Difference Between Map and HashMap in Java?

Map is an interface and HashMap is a class that implements Map interface. Map is a useful data structure in Java that stores key-value pairs. The keys are used to retrieve values stored in the map. There are three main differences between Map and HashMap in Java.

• Performance: HashMap provides faster performance than Map since it uses a hash table for storing items. On the other hand, Map may slow down when the size of the map grows since it uses a list to store items.
• Null Keys: Map doesn't allow null keys while HashMap allows one null key and multiple null values.
• Immutability:Map is immutable, meaning that its contents cannot be changed after they have been added. On the other hand, HashMap is mutable, meaning that its contents can be changed.

In conclusion, Map and HashMap are two different implementations of the same interface and they both store key-value pairs. However, HashMap provides faster performance and allows for null keys, so it is usually preferred over Map in most cases.