Java’s standard library is powerful, but in real-world projects, developers often rely on additional tools and libraries to simplify development, testing, data handling, and integration with other systems.

In this chapter, we explore some of the most commonly used Java libraries and tools that act as practical extensions to the core JDK. These tools are not part of Java SE but are considered essential in professional Java development.

You’ll get introduced to:

• Build and dependency management using Maven
• Writing unit tests with JUnit
• Handling JSON with Jackson, Gson
• Using logging frameworks like Log4j, SLF4J, Logback
• Utility libraries like Apache Commons, Guava
• HTTP clients like OkHttp, Apache HttpClient
• Dependency injection and lightweight frameworks

Each section will introduce the library/tool, explain when and why to use it, and provide simple usage examples to help you integrate them into your Java applications.