How to Retrieve a Specific Value From a HashMap Using Key?

A HashMap is a data structure that implements a map interface in Java. It stores key-value pairs. On the key object's hashcode, it uses a hashing function for computing an index-based element. And it is used to store and retrieve values. This allows very fast lookup, addition, and removal of key-value pairs, with average O(1) time complexity.

In this article, we will learn how to retrieve a specific value from a HashMap using its key in Java.

Syntax:

HasMap.get(object key_element)

Program to Retrieve a Specific Value From a HashMap Using Key in Java

Below is the implementation of retrieving a specific value from a HashMap using its key:

// Java Program to to retrieve a specific value from a HashMap using its key
import java.util.HashMap;
public class Main 
{
  public static void main(String[] args) 
  {
    
    // Create a HashMap
    HashMap<String, Integer> courses = new HashMap<>();
    
    // Add key-value pairs
    courses.put("Java", 30000); 
    courses.put("C++", 25000);
    courses.put("Python", 35000);
    
    // Retrieve value using key
    String key = "Java";
    Integer value = courses.get(key); 
    
    System.out.println(value); 
  }
}

30000

Explanation of the above Program:

• In the above program, a HashMap is created to store String keys and Integer values.
• Key-value pairs are added using the put() method.
• The key "Java" is used to retrieve the value.
• The get() method is called on the map, passing the key as a parameter.
• This returns the Integer value mapped to "Java", which is 30000.
• The value is printed to verify it was retrieved correctly.

Note: The get() method returns the value or null if key is not found.