HappyCoders

Combined Training Java 17 + 21: Records, Virtual Threads & All New Features Since Java 11

Many teams are still working with Java 11 – leaving six years of Java innovations untapped. Records, Sealed Classes, and Pattern Matching make code easier to understand and maintain. Virtual Threads fundamentally simplify highly scalable applications.

In four days, this combined training brings your team up to the level that Java 21 makes possible –
all the key innovations from Java 12 to 21, clearly explained and immediately applicable.

Request now – no obligation
4 days
Individual date
On-site or online
German / English
Customizable content
Certificate of completion

What you’ll learn in this training

In this 4-day intensive course, you’ll learn all relevant innovations introduced in Java versions 12 to 21 – compactly, clearly, and with a strong focus on practical application in everyday project work.

Discover how modern language features like Records, Switch Expressions, Text Blocks, Pattern Matching for instanceof, and Sealed Classes can make your code more elegant and maintainable.

You’ll also explore valuable additions like Helpful NullPointerExceptions and new methods in core APIs such as String, Stream, and Files.

We’ll also cover Garbage Collection improvements (G1, Parallel GC, ZGC, Shenandoah) and performance enhancements like CDS Archives and specialized TreeMap implementations.

In the second part, you’ll explore features introduced in Java 18 to 21 – including Virtual Threads, Record Patterns, and Pattern Matching for switch, enabling more concise and expressive logic.

You’ll also get to know the Sequenced Collections API, UTF-8 by default, the Simple Web Server, and more improvements across standard APIs.

Once again, we’ll dive into Garbage Collector enhancements (especially Generational ZGC) and performance features like alternative locking mechanisms.

Through practical exercises based on real-life scenarios, you’ll immediately apply what you’ve learned and anchor your knowledge.

The course concludes with a look at preview features in Java 21: Structured Concurrency, Scoped Values, the Foreign Function & Memory API, and the Vector API – a glimpse into Java’s exciting future.

Target audience

This course is for Java developers who want to stay current – hands-on, accessible, and packed with “aha” moments.

Whether you’re planning a migration to Java 17 or 21, or you already have first-hand experience – this combo course gives you a comprehensive understanding of the latest LTS versions.

If you want to take the step to Java 25 right away, you’ll find the right offer in the Combined Training Java 21 + 25 – or cover all three LTS versions in the Combined Training Java 17 + 21 + 25.

Agenda

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 ByteBuffer 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:

  • Generational ZGC
  • Alternative fast-locking scheme

Deprecations & Removals:

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

Looking Ahead:

  • Structured Concurrency
  • Scoped Values
  • Vector API
  • Foreign Function & Memory API
  • Unnamed Patterns and Variables
  • Compact Classes and Instance Main Methods

Does this sound interesting for your team?

Request now – no obligation

Why learn with me?

I’ve been working with Java for over 20 years – as a developer, CTO, trainer, author, and speaker – and have helped companies modernize complex Java systems and develop their teams sustainably.

With HappyCoders.eu, I’ve built one of the most widely read Java blogs in the German-speaking world, and I regularly speak at conferences and user groups.

I know both parts of this course – Java 17 and Java 21 – inside out: I’ve covered virtual threads, records, and sealed classes in depth on HappyCoders, and Pattern Matching for switch in Java Magazin.

My goal: to teach complex topics in a way that is understandable, practical, and immediately applicable.

Rated 4.97 out of 5 on ProvenExpert

More about me

Any questions?

Participation & Booking

Can individuals book this training?

This training can only be booked for teams. If you’d like to attend as an individual, I offer two courses (in German) through ppedv:

How many participants are possible?

I recommend a maximum of 12 participants per training – that way I can give everyone individual attention. There is no minimum: I charge per training, not per person.

How does booking work?

The easiest way is the request form or an email to schulung@happycoders.eu. Right after submitting, you can book a video call via Calendly, where we discuss the details. You’ll then receive a concrete offer from me.

Prerequisites

What prior Java experience is required?

Ideally, you’re familiar with Java 11. If you’ve worked with Java 8, you’ll be able to follow along just fine – the most important differences are put into context during the course. In general, I recommend at least two years of hands-on experience with Java.

What technical requirements do we need?

All participants need an up-to-date IDE with at least Java 21 – I use IntelliJ IDEA myself. Java 21 or later should also be installed in the terminal, as we’ll run some of the exercises there.

Schedule & Content

What does a training day look like?

Each day has six hours of net training time – usually with two short breaks and a longer lunch break in between. We align the exact schedule with your working hours – that’s flexible.

How much time is theory, how much is practice?

About half theory, half practice: a short theory phase is followed directly by applying it to code – with examples from real projects. Listening alone doesn’t help much; the knowledge has to be used immediately for it to stick.

Can we adjust or prioritize individual agenda topics?

Yes, that’s no problem. Dropping topics or weighting them differently – as long as I don’t have to restructure the training materials, there are no extra costs.

If you need more extensive changes – for example, combining content from different courses or adding entirely new topics – I’ll be happy to prepare an individual offer.

What exactly does “customizable content” mean?

Within the existing agenda, the weighting can be adjusted: shortening topics, setting priorities, changing the order. That’s free of charge.

Beyond that, more far-reaching adjustments are possible – such as combining content from different courses or completely new topic blocks. This involves extra effort, so I’ll prepare an individual offer for it.

Format & Materials

Which platform do we use for virtual training?

We usually use Zoom. If you prefer your own platform – for example, Microsoft Teams or Google Meet – I’m happy to work with that. Just let me know in advance.

Do participants receive materials to keep?

Yes. Before the training, you’ll receive the exercises as a Git repository so you can get started right away. After the training, you’ll also receive the slides – including all solutions to the exercises.

Prices & Costs

What do the travel expenses include?

Travel expenses are charged as a flat rate – depending on the training location and the number of overnight stays required. The exact amount is part of the individual offer I’ll send you.

Are there discounts for booking multiple trainings?

Yes. For multiple booked trainings or follow-up bookings, I can offer a volume discount. We’ll discuss this in the video call, and I’ll include it in the offer.

Is this a good fit for your team?

Just write to me – I usually reply within 24 hours.
Or book a free video call right away, and we’ll discuss everything important.

Request now – no obligation

Related trainings

Mastering Java 17 – All New Features Since Java 11

Learn the most important features introduced in Java 12 to 17 – including switch expressions, text blocks, records, and pattern matching. With practical examples for productive use in everyday development.

2 days On-site / online German / English

Mastering Java 21 – All New Features Since Java 17

Get ready for Java 21! Virtual threads, structured concurrency, pattern matching for switch, record patterns, sealed classes, and more. Hands-on and clearly explained, with many exercises for modern Java development.

2 days On-site / online German / English

Combined Training: Java 21 + 25

Learn all essential updates from Java 17 to 25 in just four days – practical, clear, and full of examples for applying modern Java features in your daily projects.

4 days On-site / online German / English

Combined Training: Java 17 + 21 + 25 (Intensive)

This six-day intensive training covers all updates since Java 11 – packed with hands-on examples and real-world applicability. Perfect for teams needing a full update after a longer break.

6 days On-site / online German / English

Combined Training: Java 17 + 21 + 25 (Compact)

Learn all important updates since Java 11 in just five days – delivered more compactly and with a focus on the features most relevant for everyday development.

5 days On-site / online German / English