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Combined Training Java 17, 21, and 25 – Compact (5 Days)

Duration: 4 days
–
Format: virtual or on-site

Overview

In this 5-day compact course, you’ll learn all essential updates from Java 12 through 25 – in a structured, accessible, and practical format.

Java 17 Module Highlights:

Get to know features like Records, Switch Expressions, Text Blocks, Pattern Matching for instanceof, and Sealed Classes, along with enhancements in core APIs and Garbage Collection (including ZGC and Shenandoah).

Java 21 Module Highlights:

Deepen your knowledge with Virtual Threads, Record Patterns, Pattern Matching for switch, and the new Sequenced Collections API. Additional topics include API enhancements, Generational ZGC, and memory/performance optimizations.

Java 25 Module Highlights:

Explore modern innovations such as Unnamed Variables & Patterns, Stream Gatherers, Scoped Values, and Markdown Documentation Comments. The Foreign Function & Memory API enables secure native integration. More highlights: Compact Source Files, Instance Main Methods, and advanced performance features.

Exercises & Outlook:

Apply your new knowledge in practical, real-world inspired exercises and gain insight into what’s coming next: Primitive Types in Patterns, Structured Concurrency, Stable Values, and the ongoing evolution of the Vector API.

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Target Audience

This course is designed for Java developers who want a complete, up-to-date overview of Java 17, 21, and 25 – all in one go.

Perfect if you’re planning to migrate, already using Java 25, or want to bridge the gap after skipping several Java versions.

Course Details

Duration: 5 days (optionally: 6 days)
Date by arrangement
Exclusively for your team
Delivered on-site or online
Customizable content
Language: English or German
Certificate of completion included

Pricing

On-site:  € 9.960,–
plus trainer travel expenses
Virtual:  € 8.200,–
Prices exclude VAT and any customization fees.

Agenda

We won’t follow the listed order strictly. Instead, we’ll alternate between major features, smaller topics, and theory – keeping the course engaging and balanced, and helping you better retain the material.

Part 1: Java 12-17

Major Features:
  • switch Expressions
  • Text Blocks
  • Records
  • Pattern Matching for instanceof
  • Sealed Classes
  • Strongly Encapsulate JDK Internals
Additional Enhancements:
  • Helpful NullPointerExceptions
  • Hidden Classes
  • Warnings for value-based classes
  • Context-specific deserialization filters
API Improvements:
  • New String methods
  • New Stream methods
  • New Files methods
  • New ByteByffer methods
  • The Teeing collector
  • Hex formatting and parsing utility
Garbage Collection:
  • Improvements to G1 and Parallel GC
  • New: ZGC and Shenandoah
  • Elastic Metaspace
Performance
  • Default and dynamic CDS archives
  • Non-volatile mapped byte buffers
  • Specialized TreeMap implementations
  • Decoupling of Compressed Oops and Compressed Class Pointers
Tools:
  • JFR event streaming
  • Packaging tool
Deprecations:
  • Thread suspend(), resume()
  • ThreadGroup stop(), destroy(), isDestroyed(), setDaemon(), and isDaemon()
  • Biased locking
  • And more...

Part 2: Java 18-21

Major Features:

  • Virtual Threads
  • Sequenced Collections
  • Record Patterns
  • Pattern Matching for switch

Additional Features:

  • UTF-8 by default
  • Simple web server
  • Code snippets in Java API documentation
  • New system properties for System.out and System.err encoding
  • Compiler warnings for lossy type casts
  • Key Encapsulation Mechanism API

Bugfixes:

  • IdentityHashMap's remove() and replace() methods use object identity

API Enhancements:

  • New methods for String, StringBuilder, and StringBuffer
  • New methods for Character
  • New methods for Math
  • HashMap.newHashMap()
  • Additional date-time formats

Garbage Collection:

  • String deduplication for ZGC, SerialGC, ParallelGC
  • G1 enhancements
  • Generational ZGC

Performance:

  • Alternative fast-locking scheme

Deprecations & Removals:

  • Deprecate finalization for removal
  • Locale constructors
  • URL constructors
  • Thread.stop(), suspend(), resume()
  • ThreadGroup
  • Dynamic loading of agents

Part 3: Java 22-25

Major Features:

  • Unnamed Variables & Patterns
  • Foreign Function & Memory API
  • Markdown Documentation Comments
  • Stream Gatherers
  • Synchronize Virtual Threads without Pinning
  • Scoped Values
  • Compact Source Files and Instance Main Methods

Other New Features:

  • Module Import Declarations
  • Launch multi-file source-code programs
  • Console methods with explicit Locale
  • Class-File API
  • Key Derivation Function API

API Enhancements:

  • Locale-dependent list patterns
  • Support for Duration until another Instant

Garbage Collection:

  • G1 GC improvements
  • ZGC: Generational mode by default

Performance / Memory Footprint:

  • Compact Object Headers
  • Ahead-of-Time Class Loading & Linking
  • Relax alignment of array elements
  • Change LockingMode default from LM_LEGACY to LM_LIGHTWEIGHT
  • Linking run-time images without JMODs

Deprecations & Removals:

  • Thread.countStackFrames()
  • Old core reflection implementation
  • Deprecations and removals in sun.misc.Unsafe
  • Thread.suspend(), resume() und ThreadGroup.suspend(), resume(), stop()
  • Security Manager

Looking Ahead:

  • Primitive Types in patterns, instanceof, and switch
  • Stable Values
  • Vector API
  • Structured Concurrency

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Inquiry Training Specific Course (#31)

Your Trainer: Sven Woltmann

Sven Woltmann

I’m a Java expert with over 20 years of experience – as a developer, architect, CTO, performance coach, and trainer.

I’ve designed enterprise-scale systems for companies like 1&1, IONOS, and ICE Services, modernized legacy apps, and helped teams build robust, maintainable, and high-performance Java software.

With HappyCoders.eu, I’ve built one of the most widely read Java blogs in the German-speaking world. I speak at conferences and Java User Groups – and often receive praise for making complex technical topics easy to understand.

What you’ll get from my courses:

  • Extensive experience: Deep Java knowledge with real-world expertise
  • Practical focus: Plenty of hands-on exercises drawn from actual project work
  • Knowledge sharing: Space for your questions, discussions, and real-life challenges
  • Tailored to your team: Content can be flexibly adapted to your goals

I don’t just teach features – I show you how to develop better software with a deep understanding of Java.

More about me »

Format & Requirements

  • Learning method: Short theory blocks followed by immediate hands-on practice – with exercises, code examples, and real-world scenarios.
  • Materials: All course materials (slides and code) are provided at the beginning of the course.
  • Adaptability: I adjust the course pace to the group’s knowledge level when needed. In some cases, not all topics may be covered in full.
  • Technical requirements: Your own laptop or workstation with Java 21 (or later) and an IDE (I recommend IntelliJ IDEA).

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