Java Compact Source File: No Class, No Static Main
Java compact source file example – a Java file with no class and no public static void main. Learn instance main methods, the IO class, and the launch order, with full runnable code and real output.
Java Scoped Values Example
Learn Java scoped values (JEP 506) with simple, runnable examples. See the problem they solve, how other languages do it, and how to share data with callees and child threads without method parameters. Tested with Java 25.
Spring Boot RAG Example with Spring AI
Learn RAG (Retrieval Augmented Generation) in Spring Boot with Spring AI. Load your own notes into a vector store and let the AI answer questions about them.
Java AtomicInteger Example
Learn Java AtomicInteger with simple examples, tested on Java 25. See why a normal int breaks with threads, and how incrementAndGet, compareAndSet and updateAndGet fix it.
Java Virtual Threads Example
Learn Java virtual threads with simple, runnable examples on Java 25. Start one virtual thread, run 10,000 tasks at once, and see how virtual threads fix a slow thread pool without rewriting your code.
Spring Boot Supabase CRUD Example
Connect Spring Boot 4.1.0 to a free Supabase PostgreSQL database with Spring Data JPA. Full CRUD REST API, unit tests, and real output.
Spring Boot REST Docs Example
Learn how to document a Spring Boot REST API with Spring REST Docs. Your tests write the documentation. Full working Book Manager example with code and output.
How to Install Java on Windows (Step-by-Step Guide)
Learn how to install Java 21 (Oracle and Temurin) on Windows with screenshots and easy-to-follow instructions.
Micronaut + Flyway Database Schema Migrations
Learn how to integrate Flyway with Micronaut to manage database schema migrations effortlessly. This guide covers Flyway scripts, PostgreSQL, Docker, and full CRUD examples with tests.
Micronaut Logging using Log4j2
In this article, we show how to set up and use Log4j2 for logging in a Micronaut application.
List all available features in the Micronaut CLI (mn)
In the Micronaut CLI mn, we can use mn create-app –list-features to list all available features. Table of Contents 1. List All Feature 2. Filter Features 3. Download Source Code 4. References P.S. Tested with Micronaut 4.7.6 1. List All Feature Terminal mn create-app –list-features This will output a categorized list of features like: Terminal […]
Micronaut Logging using Logback
Discover how to efficiently implement logging in your Micronaut applications using default Logback framework. Logging to the console, standard files, and rolling files with practical examples.
Return ZIP file in a Micronaut Controller
In this tutorial, we will create a Micronaut REST API that generates and returns a ZIP file for download. Table of contents 1. Create a Micronaut Controller 2. Unit Testing the Controller 3. Run the Application 4. Download Source Code 5. References Technologies used: Java 21 Micronaut 4.7.6 Maven 3.9.6 1. Create a Micronaut Controller […]
Working Gzip and tar.gz file in Kotlin
This article shows how we can compress, update, and decompress multiple files and folders into a tar.gz file using Kotlin. Table of contents: 1. Gzip vs. Java Zip 2. Add Apache Commons Compress Dependency 3. Compressing Files and Folders into a tar.gz 3.1 file name is too long (>100 bytes) 4. Decompressing a tar.gz File […]
How to compress and decompress zip file in Kotlin
In this tutorial, we’ll explore how to create ZIP files, add multiple files and folders to a zip file, add files to an and decompress files using Kotlin. Table of contents: 1. Adding Multiple Files to a ZIP File 2. Adding Multiple Folders to a ZIP File 3. Adding Multiple Files or Directories to an […]
Return Excel file in a Micronaut Controller
In this tutorial, we will learn how to return a Excel file .xlsx in a Micronaut controller using Apache POI. Table of contents 1. Add Apache POI Dependency 2. Create the Excel Service 3. Create the Controller to return Excel file 4. Run the Application 5. Testing the Excel Download Endpoint 6. Download Source Code […]
Return PDF file in a Micronaut Controller
In this tutorial, we will create a Micronaut REST API that generates and returns a PDF file using OpenPDF. Table of contents 1. Add OpenPDF Dependency 2. Creating the PDF Controller 3. Testing the API 4. Writing Unit Tests 5. FAQs 6. Download Source Code 7. References Technologies used: Java 21 Micronaut 4.7.6 Maven 3.9.6 […]
How to Run Startup Code When Micronaut Starts
When building applications with Micronaut, we often need to execute some logic when the application starts. This could include tasks like initializing resources, seeding a database, or logging system information. In this article, we will explore how to run startup code in Micronaut using ApplicationEventListener and @EventListener. Table of contents 1. Implements ApplicationEventListener to Run […]
Return JSON in a Micronaut Controller
In this tutorial, we will learn how to return JSON in a Micronaut controller using simple and practical examples. Table of contents 1. Setting Up the Micronaut Project 2. Returning a JSON Object Define a Data Model What is @Serdeable? Create a Controller Run the Application 3. Returning a List of JSON Objects Run the […]
How to Use Dependency Injection in Micronaut
Learn how to effectively use dependency injection in Micronaut with real-world examples, covering constructor injection, multiple implementations, field injection, method injection, and unit testing.
Micronaut – Loading external yaml or configuration file
In this tutorial, we will explore how to load an external YAML file in a Micronaut application. Table of contents 1. Why Load External Configuration Files? 2. Defining an External YAML File 3. Configuring Micronaut to Load the External YAML File Using Command Line Argument Using Environment Variable 4. Accessing Configuration Values in Micronaut Using […]
Kotlin – Reading Large Files Efficiently
When working with large files in Kotlin, handling them efficiently is crucial to avoid performance issues such as high memory usage and slow processing times. In this article, we explore different approaches to reading large files efficiently in Kotlin and compare them with Java. Table of contents Why Efficient File Reading Matters 1. Read Large […]
Kotlin – Read, Write, Modify, Delete, and List Files
In this article, we will cover how to read, write, modify, delete, and list files in Kotlin and compare them with Java equivalents. Table of contents 1. Reading a File in Kotlin 2. Writing to a File in Kotlin 3. Modifying a File in Kotlin 4. Deleting a File in Kotlin 5. Listing Files in […]
Micronaut @ConfigurationProperties Example
Micronaut provides a powerful way to manage configuration using @ConfigurationProperties. This annotation allows us to bind external configuration properties (such as values from application.yml or application.properties) directly to Java objects. Table of contents 1. Setting Up the Micronaut Project 2. Defining Configuration in application.yml 3. Setting Up the Configuration 4. Injecting the Configuration into a […]
Micronaut @ConfigurationBuilder Example
Micronaut @ConfigurationBuilder allows us to bind configuration files to Java objects using builder pattern. Table of contents 1. Defining Configuration in application.yml 2. Builder Pattern 3. Using @ConfigurationBuilder 4. Injecting the Configured Database 5. Running the Application 6. Unit Tests 7. Download Source Code 8. References Technologies used: Java 21 Micronaut 4.7.6 Maven 3.x 1. […]
Micronaut Tutorials
List of the Micronaut examples, updating still in progress… 1. Getting Started Micronaut Hello World Example Micronaut @ConfigurationProperties Example Micronaut @ConfigurationBuilder Example Micronaut Loading external yaml or configuration file How to Use Dependency Injection in Micronaut Return XML in a Micronaut Controller Return JSON in a Micronaut Controller Return PDF in a Micronaut Controller Return […]
Micronaut Hello World Example
Learn how to create a simple “Hello, World!” application using the Micronaut framework
How to install Micronaut CLI
Learn how to install Micronaut CLI on Windows, macOS, and Linux using SDKMAN!, Homebrew, Chocolatey, or manual installation.
How to Prevent java.lang.OutOfMemoryError in Java
Encountering a java.lang.OutOfMemoryError can be frustrating, but we can take several practical steps to prevent it. In this article, we explain what causes this error, provide real world examples, and discuss effective techniques to manage memory in our Java applications. Table of contents Understanding java.lang.OutOfMemoryError Common Causes and Prevention Techniques 1. Optimize Heap Size 2. […]
Kotlin – Use `object` for Singleton Patterns
In software development, a singleton is a design pattern that ensures a class has only one instance and provides a global access point to it. While implementing singletons in Java requires additional effort, Kotlin makes it simpler using the object keyword. In this article, we will learn how to create a singleton in Kotlin using […]
Top 10 Java Frameworks to Watch in 2025
Java remains one of the most powerful and versatile programming languages, widely used in enterprise applications, web development, microservices, and cloud-based solutions. As technology evolves, new frameworks continue to emerge, improving development efficiency, scalability, and security. In this article, we explore the top 10 Java frameworks to watch in 2025. Java Frameworks 2025 Framework Microservices […]
Return XML in a Micronaut Controller
In this tutorial, we will learn how to return XML responses in a Micronaut application using Jackson XML. Table of contents 1. Setting Up the Micronaut Project Add Jackson XML Dependency 2. Creating the XML Model 3. Creating a Controller to Return XML 4. Running and Testing the Application 5. Writing Unit Tests 6. Download […]
Top 10 Java Application Servers for 2025
Java application servers play a crucial role in deploying and managing Java-based applications. They provide essential features such as security, transaction management, scalability, and performance optimization. In this article, we explore the top 10 Java application servers that developers and enterprises commonly use. Java Application Servers Server Jakarta EE Support Cloud-Native Performance Scalability Use Case […]
Kotlin – Use val Instead of var Wherever Possible
When writing Kotlin code, you should prefer using val instead of var whenever possible. This simple practice enhances code safety, improves performance, and makes your code easier to read and maintain. In this article, we’ll explore why val is preferable, how it compares to var, and provide real-world examples, including a comparison with Java. Table […]
Kotlin – Using ?. and ?.let {} to Avoid Null Checks
One of the most common issues in Java programming is dealing with null values, which can lead to the dreaded NullPointerException (NPE). Kotlin, however, provides built-in features to handle null safety in a more elegant way. Two of the most useful tools for this are ?. (safe call operator) and ?.let {} (scope function). In […]
Zip4j – Java Library for ZIP Files (With Examples)
In this tutorial, we show how to use the Zip4j library for handling ZIP files like adding files and directories, updating existing ZIPs, password protection, and encryption. Table of Content: 1. Adding Zip4j Dependency 2. Creating a ZIP File and Adding Files 3. Adding a Directory to ZIP 4. Adding Files to an Existing ZIP […]
How to Check if a File Exists in Kotlin
In Kotlin, we can use the `File` built-in `exists()` method to check if a file exists.
Java – Swap Two Variables Without a Temp Variable
Swapping two variables is a common task in programming. Traditionally, we use a temporary variable to hold one value while swapping, but Java allows us to swap two variables without using a temp variable. In this tutorial, we will explore different ways to achieve this in Java with real-world examples. Table of contents: 1. Swapping […]
How to Change the Default Micronaut Server Port
By default, a Micronaut application runs on port 8080. In this guide, we will explore multiple ways to change the default Micronaut server port. Table of Contents: 1. Changing the Server Port in application.yml 2. Changing the Server Port in application.properties 3. Setting the Port Using Environment Variables 4. Setting a Random Port 5. Download […]
How to Replace Spaces with Dashes in Java
We can use the Java String built-in `replace()` or `replaceAll()` methods to replace spaces with dashes (`-`) easily.