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JDK8 to 25 - A practical migration guide
This book is 100% completeLast updated on 2026-09-02
Migrating from JDK 8 to a modern Java release crosses years of platform change, and the hardest failures are not always the ones that stop your application. This practical guide shows you how to find what will break, understand why, and fix it systematically using real tools, reproducible examples, and a failure catalogue built around the problems Java teams actually hit.
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About
About the Book
Moving a Java application from JDK 8 to a modern JDK is not a simple version bump. Across the releases in between, APIs have disappeared, defaults have changed, internals have been locked down, build tools have moved on, and code that still compiles can behave differently at runtime.
This book is a practical guide to finding those problems before they find you. It explains the tools you can use to assess an existing application, maps the important changes across JDK releases, and provides a catalogue of real migration failure modes: what they look like, why they happen, how to detect them and what to do about them.
The focus is on getting from JDK 8 to JDK 25, while also showing what JDK 26 changes next. The examples are built around real JDK behaviour and are designed to be used as much as read. You can work through the guide as part of a planned migration, or jump straight to the failure, exception or behaviour you are trying to understand.
The aim is simple: replace “let’s upgrade it and see what breaks” with a migration you can investigate, test and manage.
Author
About the Author
Steve Poole
Steve Poole has engineered Java SDKs and JVM runtimes since the platform's initial releases. Over a multi-decade career at IBM, he developed and delivered enterprise Java runtimes, represented IBM across numerous Java Specification Requests (JSRs), and contributed to core open-source initiatives across Apache, Eclipse, and OpenJDK. He was an early participant in the Adopt OpenJDK initiative, advocating for broader community participation in OpenJDK testing and distribution.
He is a Java Champion, Oracle ACE, IBM Champion, and a director of the London Java Community (LJC). He has delivered technical presentations on JVM internals, runtime diagnostics, and memory architectures at international developer conferences, including JavaOne, Devoxx, JAX, and QCon.
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