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Java 21 to 25: What's New for the 1Z0-831 Exam
New
2 students

Java 21 to 25: What's New for the 1Z0-831 Exam

Every Java 22-25 feature the 1Z0-831 exam can test, with the traps, for developers who already know Java 21
Created byStephen Leonard
Last updated 10/2026
English
English

What you'll learn

  • Use every Java 22-25 language feature that is final in JDK 25 and on the 1Z0-831 exam
  • Spot the compile errors the exam builds questions around, before running the code
  • Write and compose Stream Gatherers, and predict their output on ordered and parallel streams
  • Choose between scoped values and ThreadLocal, and explain virtual-thread pinning in Java 24+
  • Tell which Java 25 features are preview or incubator, and leave them out of your revision

Course content

9 sections • 28 lectures • 1h 38m total length

  • Welcome: who this course is for1:26
  • The 1Z0-831 exam3:20
  • Set up JDK 25 and run single-file programs3:09

Requirements

  • Solid Java 21 knowledge: records, sealed types, pattern matching for switch, virtual threads
  • JDK 25 installed if you want to run the samples (setup is covered in lecture 3)

Description

This course contains the use of artificial intelligence.

You already know Java 21, or you've passed 1Z0-830. This course covers exactly what changed in Java 22, 23, 24 and 25 that the 1Z0-831 (Java SE 25 Developer Professional) exam can test, and nothing you already know.

It's a delta course: no second pass over the Java 21 syllabus.

What's covered:

  • Compact source files, instance main methods and the new IO class in java.lang

  • Module import declarations, and the ambiguity traps they create

  • Launching multi-file source programs

  • Unnamed variables and patterns: every place _ is allowed, and every place it isn't

  • Flexible constructor bodies: what the prologue can and can't touch

  • Pattern matching and sealed types, re-checked for Java 25

  • Stream Gatherers: the five built-ins, the four functions, writing your own

  • Scoped values, and why synchronized no longer pins virtual threads

  • Markdown doc comments, the Security Manager's removal, and which preview features not to study

How it's built:

  • Every code sample on every slide was compiled and run on JDK 25. Every "this does not compile" claim was checked against the real compiler error.

  • Lectures flag the exam traps as they go, two sections end with full trap clinics in the style of exam questions, and the course closes with ten trap patterns and a walked-through mini mock.

  • Only features final in JDK 25 are taught. Preview and incubator features get one lecture explaining why you shouldn't study them.

Narration: the voice-over is AI-generated (text-to-speech), transcribed back and checked so that every technical term is pronounced correctly.

This course is not affiliated with or endorsed by Oracle. Java and Oracle are registered trademarks of Oracle and/or its affiliates.

Who this course is for:

  • Java 21 developers, or 1Z0-830 holders, preparing for the 1Z0-831 exam
  • Java developers who want a fast, exam-accurate tour of what changed in Java 22-25

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