Java Virtual Machine Series
Last updated: July 28, 2025
Mocking is an essential part of unit testing, and the Mockito library makes it easy to write clean and intuitive unit tests for your Java code.
Get started with mocking and improve your application tests using our Mockito guide:
Handling concurrency in an application can be a tricky process with many potential pitfalls. A solid grasp of the fundamentals will go a long way to help minimize these issues.
Get started with understanding multi-threaded applications with our Java Concurrency guide:
Spring 5 added support for reactive programming with the Spring WebFlux module, which has been improved upon ever since. Get started with the Reactor project basics and reactive programming in Spring Boot:
Since its introduction in Java 8, the Stream API has become a staple of Java development. The basic operations like iterating, filtering, mapping sequences of elements are deceptively simple to use.
But these can also be overused and fall into some common pitfalls.
To get a better understanding on how Streams work and how to combine them with other language features, check out our guide to Java Streams:
Explore Spring Boot 3 and Spring 6 in-depth through building a full REST API with the framework:
Yes, Spring Security can be complex, from the more advanced functionality within the Core to the deep OAuth support in the framework.
I built the security material as two full courses - Core and OAuth, to get practical with these more complex scenarios. We explore when and how to use each feature and code through it on the backing project.
You can explore the course here:
Spring Data JPA is a great way to handle the complexity of JPA with the powerful simplicity of Spring Boot.
Get started with Spring Data JPA through the guided reference course:
Refactor Java code safely — and automatically — with OpenRewrite.
Refactoring big codebases by hand is slow, risky, and easy to put off. That’s where OpenRewrite comes in. The open-source framework for large-scale, automated code transformations helps teams modernize safely and consistently.
Each month, the creators and maintainers of OpenRewrite at Moderne run live, hands-on training sessions — one for newcomers and one for experienced users. You’ll see how recipes work, how to apply them across projects, and how to modernize code with confidence.
Join the next session, bring your questions, and learn how to automate the kind of work that usually eats your sprint time.
Explore the tutorials below to understand how the Java Virtual Machine works, and how to configure the most commonly used parameters.
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JVM – Basics
- Stack Memory and Heap Space in Java
- Permgen vs Metaspace in Java
- JVM Garbage Collectors
- Generational ZGC in Java
- Weak References in Java
- Guide to the Most Important JVM Parameters
- JVM Parameters InitialRAMPercentage, MinRAMPercentage, and MaxRAMPercentage
- Differences Between Heap Dump, Thread Dump and Core Dump
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JVM – Advanced
- Native Memory Tracking in JVM
- Measuring Object Sizes in the JVM
- Difference in Used, Committed, and Max Heap Memory
- Understanding Memory Leaks in Java
- Command-Line Tools to Find the Java Heap Size
- Different Ways to Capture Java Heap Dumps
- OutOfMemoryError: GC Overhead Limit Exceeded
- Could Not Reserve Enough Space for Object Heap
- Verbose Garbage Collection in Java
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JVM – Configuration
- Choosing a GC Algorithm in Java
- Garbage Collection Logging to a File in Java
- Adding Shutdown Hooks for JVM Applications
- Configuring Stack Sizes in the JVM
- Configure the Heap Size When Starting a Spring Boot Application
- Increase the Memory Size Limit on IntelliJ IDEA
- How to Set JVM Arguments in IntelliJ IDEA?
- How to Fix java.lang.UnsupportedClassVersionError
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