Implementation of HashMap Class in Java map

The HashMap class in Java is a implementation of the Map interface that stores key-value pairs in a hash table. It allows you to store and retrieve elements based on a key, and provides constant-time performance for the basic operations (get and put).

Here is an example of how to use a HashMap in Java:

import java.util.HashMap;

public class Main {
  public static void main(String[] args) {
    // Create a HashMap
    HashMap<String, Integer> map = new HashMap<>();

    // Add some elements to the map
    map.put("apple", 1);
    map.put("banana", 2);
    map.put("orange", 3);

    // Retrieve an element from the map
    int value = map.get("banana");
    System.out.println("The value for 'banana' is: " + value);

    // Remove an element from the map
    map.remove("apple");

    // Check if the map contains a specific key
    boolean containsKey = map.containsKey("orange");
    System.out.println("The map contains the key 'orange': " + containsKey);
  }
}

In this example, we create a HashMap that maps strings (the keys) to integers (the values). We add some elements to the map, retrieve an element by its key, remove an element from the map, and check if the map contains a specific key.

Note that the HashMap class is not synchronized, which means that it is not thread-safe. If you need a thread-safe map, you can use the Collections.synchronizedMap() method to wrap a HashMap in a synchronized map.