the runtime illusion: what Java really runs

Wed, 18 Feb 2026 07:00:02 +0000

Introduction

Java’s bytecode is made abstract to be portable and neutral from specific hardware. Yet in production, it performs with the precision of native code. How? The secret lies in the JIT compiler, a near magical blend of static analysis and real-time insights. It reinterprets, restructures and often reinvents the code based on the runtime behaviour. This article traces that silent transformation using the Semeru (OpenJ9) JIT, following a method from source to bytecode to intermediate representation and ultimately to highly optimised machine code. You will be amazed to see how your logic is optimized beyond recognition. What you write is not always what runs, and what runs is often much better version of what you imagined.

Optimizing Spring Integration Tests at Scale

Wed, 17 Dec 2025 07:00:02 +0000

1. Introduction

Sprint Boot is a popular Java framework that provides a rich platform for integration testing. It’s pretty convenient and flexible; however, at a large scale, when the project has hundreds or even thousands of integration tests using lots of heavy components (like TestContainers-managed beans), there can be performance and other issues. There are many hidden details that make much sense when the codebase becomes bigger and the configuration becomes more complicated. In this article, we’ll look at how the framework works under the hood, why it can be slow and inefficient, and how to boost the performance.

Optimization on JAVAPRO International

the runtime illusion: what Java really runs

Introduction

Optimizing Spring Integration Tests at Scale

1. Introduction