Java’s journey revolutionized the tech world – now, IBM Semeru is redefining its future once again.

Nearly thirty years ago, Java transformed how software is built, and it continues to evolve. But as our applications grow more cloud-native, containerized, and performance-hungry, the old ways of running Java aren’t always enough. 

Modern Java needs a modern runtime, and that’s where IBM Semeru steps in: a fast, efficient JDK powered by OpenJ9, built for today’s development needs. Faster startups, lower memory usage, smarter cloud scaling – Semeru gives Java developers the edge they need without giving up the freedom of open source.

🔍 What Is IBM Semeru?

IBM Semeru is a high-performance, production-ready distribution of OpenJDK, the open-source implementation of the Java Platform. 
Unlike standard OpenJDK builds, Semeru has something unique under the hood: Eclipse OpenJ9, a lean, fast, and highly configurable JVM developed by IBM.

Semeru is available in two main editions:

• Open Edition – A free, open-source build ideal for most developers and teams seeking performance and reliability without vendor lock-in.
• Certified Edition – A commercially supported build, certified for Java compliance and backed by IBM’s world-class enterprise support.

Both editions are designed to be drop-in replacements for any standard OpenJDK distribution, meaning no code changes are required. The difference lies in the engine: OpenJ9 delivers a runtime performance profile optimized for today’s modern Java workloads.

Whether you are deploying Kubernetes microservices, scaling enterprise backends, or pushing cloud-native innovations, Semeru is engineered to help your Java apps run leaner, faster, and smarter.

🚀 Why Should Java Developers Care?

In a world with multiple JDK choices — Temurin, Zulu, GraalVM, Amazon Corretto — it's fair to ask: why Semeru?

The answer: measurable advantages where it matters most – performance, memory footprint, startup time, and cloud-readiness.

✨ The Perks of Using Semeru:

• Faster Startup & Smaller Footprint:
  OpenJ9 reduces JVM memory usage and cold start times – ideal for microservices and serverless functions.
• Shared Class Cache (SCC):
  A game-changing OpenJ9 feature that shares class metadata across JVM processes, improving both startup time and runtime performance, especially in containers.
• Flexible Garbage Collection Policies:
  Semeru lets you fine-tune garbage collection strategies depending on your workload, whether you need maximum throughput or minimal pause times.
• Cloud-Native Optimization:
  Semeru is optimized for platforms like Kubernetes and OpenShift, with better memory management and scaling.
• Enterprise-Grade Open Source:
  Built collaboratively by IBM and the Eclipse community, Semeru balances fast innovation with trusted long-term stability.

Semeru isn’t just another JDK – it’s a smarter, faster foundation for the future of Java development.

🧪 Semeru vs HotSpot: 

With Semeru (OpenJ9):

$ java -version
openjdk version "21.0.6" 2025-01-21 LTS
IBM Semeru Runtime Open Edition 21.0.6.0 (build 21.0.6+7-LTS)
Eclipse OpenJ9 VM 21.0.6.0 (build openj9-0.49.0, JRE 21 Mac OS X aarch64-64-Bit 20250121_371 (JIT enabled, AOT enabled))

With HotSpot (Temurin/Oracle):

$ java -version
openjdk version "21.0.2" 2024-01-16
OpenJDK Runtime Environment Temurin-21.0.2+13
OpenJDK 64-Bit Server VM (build 21.0.2+13, mixed mode)

Both are fully OpenJDK-compliant, but under the surface, OpenJ9 introduces meaningful runtime improvements designed for today’s cloud-native world.

📈 Semeru in Action

IBM has benchmarked OpenJ9 in real-world enterprise scenarios. Here's what developers can expect when they move to Semeru:

• 40–50% lower memory footprint for many Spring Boot and Jakarta EE applications compared to HotSpot.
• Up to 25% faster cold starts in cloud and containerized environments.
• Faster container startups and lighter images – perfect for Kubernetes and serverless deployments.
• 2x faster restarts with Shared Class Cache (SCC) in local and CI/CD environments.

These improvements aren’t just about production – they accelerate development workflows, testing cycles, and deployment pipelines, too.

🛠️ Using Semeru in Eclipse IDE

Getting started with Semeru inside Eclipse IDE is easy and unlocks significant performance gains.

➔ Setting up IBM Semeru JDK in Eclipse:

1. Download IBM Semeru from https://developer.ibm.com/languages/semeru-runtimes/.
2. Open Eclipse: Window > Preferences > Java > Installed JREs.
3. Add a new JRE > Standard VM > Point to your Semeru JDK install folder.
4. Name it (e.g., "Semeru OpenJ9").
5. Set it as the default JRE, or configure it per project.

➔ What you get:

• All the Semeru benefits inside your IDE.
• Faster project builds and application startups inside the IDE.
• More predictable memory usage during development.
• Seamless debugging and profiling, especially when working with OpenJ9’s memory efficiency.
• A development environment that mirrors your production cloud runtime (especially on OpenShift, Kubernetes, or a JVM-optimized cloud).

➔ Bonus Tip:

For deeper tuning, Eclipse Memory Analyzer (MAT) and OpenJ9 tools like J9dump and JITServer provide valuable insights within the Eclipse ecosystem.

💬 The Road Ahead with Semeru

The Java ecosystem is thriving, and IBM Semeru is driving its future. 
With its blazing-fast startups, lower memory consumption, and cloud-native optimization, Semeru empowers developers to build next-gen Java apps, all while staying true to the spirit of open source.

If you’re building for the next generation of applications, whether it’s cloud-native microservices, scalable enterprise systems, or lightweight serverless apps, it’s time to explore what Semeru can unlock for you.

🔗 Get started today and experience the next generation of Java development.