The purpose of this tutorial is to provide a comprehensive guide on updating keys in a HashMap in Java. As Java developers, we often encounter situations where we need to modify the keys associated with certain values in a HashMap. This tutorial aims to equip you with various methods and techniques to update keys efficiently…
Read More Java: Updating Keys in a HashMapIn Java, data types define the nature of variables and the kind of values they can hold. This is important because Java is a statically-typed language, which means that variables must be declared with their specific data types before they can be used. To accommodate this, Java provides a rich set of data types to…
Read More Convert Int to Long in JavaWhen working with strings in Java, it is essential to check if a string is null or empty. A null string refers to the absence of any value, while an empty string is a string with zero characters. Failing to handle null or empty strings appropriately can lead to unexpected errors and undesired behavior in…
Read More Check if String is Null or Empty in JavaFinding the maximum and minimum values in an array is a common requirement in various programming scenarios. It allows you to extract key insights from your data, such as identifying the highest and lowest values, or determining the range of values present. This knowledge can be utilized in numerous applications, including statistical analysis, data processing,…
Read More Finding Max and Min Values in a Java ArrayJSON (JavaScript Object Notation) is a lightweight data-interchange format that has gained significant popularity in modern web development. It provides a simple and human-readable way to represent structured data. JSON consists of key-value pairs and supports various data types, including strings, numbers, booleans, arrays, and nested objects. The importance of JSON lies in its ability…
Read More Convert Java Objects to JSONThe java.lang.UnsupportedClassVersionError is a runtime error in Java that occurs when a Java Virtual Machine (JVM) encounters a class file with a version that is not supported by the JVM. This error typically arises when there is a mismatch between the version of the JVM executing the code and the version in which the class…
Read More How to Resolve java.lang.UnsupportedClassVersionError?IMPORTANT: This information is no longer actual. Apparently it was just a bug in Spring Initializr tool and Eureka is available with Spring Boot version 3.1.0 just fine. If you’re using Spring Initializr tool for creating Spring Boot projects, you might have noticed a change. In Spring Boot version 3.1.0, the tool no longer allows…
Read More Eureka Discovery with Spring Boot 3.1.+In this tutorial, I will share with you how to implement user look-up and authentication using Keycloak’s User Storage SPI. For starters, SPI stands for Service Provider Interface, and it is a way to write extensions to Keycloak to connect to external user databases and credential stores. In this tutorial, we will make Keycloak load…
Read More Keycloak User Storage SPI Example with Remote ServiceThe @DisplayName annotation is used to provide a custom name for your JUnit 5 test method. Let’s have a look how it is used in Java code. Below, is a very simple code example of a JUnit 5 test method. Notice how the @DisplayName annotation is used to provide a custom name for the text…
Read More @DisplayName Annotation in JUnit 5When we do integration testing of our Spring Boot application, we sometimes need to make it load an alternative configuration. For example, we might need to run and test our application on a different port number, make it connect to a database as a different user or even make it connect to a different database.…
Read More @TestPropertySource Annotation ExampleIf you are using Docker Desktop on Windows 10, you might encounter an error message that says “Docker Desktop stopped”. This can be frustrating and prevent you from running your containers and applications. In this tutorial, I will explain what causes this error and how to solve it in four easy steps. Step 1: Enable…
Read More How to Fix Docker Desktop Stopped Error on Windows 10Docker is a popular tool for creating and running containers, which are isolated environments that can run applications and services without affecting the host system. Docker makes it easy to deploy, manage, and scale your applications across different platforms and environments. In this tutorial, I will explain how to install Docker on Ubuntu 22.04, which…
Read More How to Install Docker on Ubuntu 22.04This tutorial will guide you through the process of running Unit Tests and Integration Tests separately in a Maven-based Spring Boot application. We will use the JUnit Tag feature to group our test cases and separate Unit Tests from Integration Tests. To learn more, check out the Test Java code tutorials page. Create your tests…
Read More Running Unit Tests and Integration Tests Separately in Spring BootIn this tutorial, you will learn how to use the @Tag annotation in JUnit 5 for organizing and running your unit tests. By the end of this tutorial, you’ll have a solid understanding of the @Tag annotation, its benefits, and how to apply it effectively in your own test cases. Let’s dive in! What is…
Read More @Tag Annotation: Organizing and Running Tests in JUnit 5If you’re an absolute beginner looking to learn about integration testing for Spring Boot applications with a MySQL database server, then you’re in the right place. As you proceed through this tutorial, remember that everyone was once a beginner, and the only silly question is the one you don’t ask. This tutorial aims to introduce…
Read More Integration Testing with Spring Boot, MySQL and Testcontainers