Java HashMap get() Method

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The HashMap.get(Object key) method in Java is used to retrieve the value associated with a specific key in a HashMap. This guide will cover the method's usage, explain how it works, and provide examples to demonstrate its functionality.

Table of Contents

1. Introduction
2. get Method Syntax
3. Examples
   • Retrieving Values from a HashMap
   • Real-World Use Case: Employee Detail Lookup
4. Conclusion

Introduction

The get(Object key) method is a member of the HashMap class in Java. It allows you to retrieve the value associated with a specific key in the HashMap. If the key is not found, the method returns null.

get() Method Syntax

The syntax for the get method is as follows:

public V get(Object key) 

• The method takes a single parameter key of type Object, which represents the key whose associated value is to be returned.
• The method returns the value associated with the specified key, or null if the map contains no mapping for the key.

Examples

Retrieving Values from a HashMap

The get method can be used to retrieve the value associated with a specific key in a HashMap.

Example

import java.util.HashMap; public class GetExample { public static void main(String[] args) { // Creating a HashMap with String keys and Integer values HashMap<String, Integer> people = new HashMap<>(); // Adding entries to the HashMap people.put("Ravi", 25); people.put("Priya", 30); people.put("Vijay", 35); // Retrieving values from the HashMap Integer ageRavi = people.get("Ravi"); Integer ageAmit = people.get("Amit"); // Key "Amit" does not exist // Printing the results System.out.println("Age of Ravi: " + ageRavi); System.out.println("Age of Amit: " + ageAmit); // This will print "null" } } 

Output:

Age of Ravi: 25 Age of Amit: null 

Real-World Use Case: Employee Detail Lookup

In a real-world scenario, you might use the get method to look up employee details based on their employee ID.

Example

import java.util.HashMap; public class EmployeeDetailLookup { public static void main(String[] args) { // Creating a HashMap with String keys (employee IDs) and String values (employee names) HashMap<String, String> employeeDatabase = new HashMap<>(); // Adding entries to the HashMap employeeDatabase.put("E001", "Ravi Kumar"); employeeDatabase.put("E002", "Priya Sharma"); employeeDatabase.put("E003", "Vijay Singh"); // Employee ID to be searched String employeeIdToSearch = "E002"; // Retrieving employee details from the database String employeeName = employeeDatabase.get(employeeIdToSearch); // Checking if the employee ID exists if (employeeName != null) { System.out.println("Employee ID " + employeeIdToSearch + " corresponds to: " + employeeName); } else { System.out.println("Employee ID " + employeeIdToSearch + " does not exist in the database."); } } } 

Output:

Employee ID E002 corresponds to: Priya Sharma 

Conclusion

The HashMap.get(Object key) method in Java provides a way to retrieve the value associated with a specific key in a HashMap. By understanding how to use this method, you can efficiently access values stored in a HashMap based on their keys. This method is useful in various scenarios, such as looking up employee details or retrieving specific data points based on unique identifiers.