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Practical Demos

This guide highlights examples that are especially useful for study, demos, and interviews because they turn a Java platform feature into a small, focused walkthrough.

Use this guide when you want a practical tour through the repository instead of reading every package in release order.

Before a study session, interview walkthrough, or live demo, run the complete practical demo check:

make demos

The table mirrors the focused checks run by make demos and also includes focused commands for running one demo at a time.

How To Use This Guide

For each feature:

  1. Read the package README first.
  2. Inspect the example class.
  3. Run the focused test command.
  4. Compare the feature with the version README and the JEP Index.

The tests keep each demo honest. They show the expected behavior without requiring a large application.

Demos

Java Feature Package or class What it demonstrates Focused test command Local requirements
18 Simple Web Server simple_web_server Starts a local static-file server with SimpleFileServer, serves a temporary directory, and verifies HTTP responses. mvn -Dtest=SimpleStaticFileServerTest test Binds a local loopback port.
18 JavaDoc snippets javadoc_snippets Shows JavaDoc @snippet markup in real generated documentation. mvn -Dtest=JavaDocSnippetExamplesTest test Run make docs to inspect rendered snippets.
21 Key Encapsulation Mechanism API key_encapsulation Establishes shared secret material with encapsulation and decapsulation. mvn -Dtest=KeyEncapsulationExchangeTest test Requires a JDK/provider with the demonstrated KEM algorithm.
22 Foreign Function and Memory API foreign_function Calls native C library functions from Java using the final FFM API. mvn -Dtest=ForeignFunctionExamplesTest test Requires native access and standard platform C library symbols.
24 Stream Gatherers StreamGatherersExamples Demonstrates final Stream Gatherers with fixed windows and running scans. mvn -Dtest=StreamGatherersExamplesTest test No external setup.
24 Class-File API class_file Parses compiled .class bytes with ClassFile.of().parse(...) and summarizes metadata. mvn -Dtest=ClassFileInspectorTest test No external setup.
24 ML-KEM / ML-DSA quantum_resistant_crypto Demonstrates module-lattice key encapsulation and digital signatures. mvn -Dtest=ModuleLatticeCryptoExamplesTest test Requires a JDK/provider with ML-KEM and ML-DSA support.
25 Scoped Values scoped_values Shows temporary scoped bindings for contextual data and verifies that the value is unbound afterward. mvn -Dtest=ScopedValuesExamplesTest test JDK 25.
25 Flexible Constructor Bodies FlexibleConstructorBodiesExamples Demonstrates validation and normalization before constructor delegation. mvn -Dtest=FlexibleConstructorBodiesExamplesTest test JDK 25.
25 Key Derivation Function API key_derivation Derives independent keys from shared secret material with HKDF. mvn -Dtest=HkdfKeyDerivationExampleTest test Requires JDK 25 KDF support.

Why These Demos Matter

These demos are useful because they go beyond syntax. They show Java evolving as a platform:

  • local tooling for static files and documentation
  • cryptography APIs for modern and post-quantum security
  • native interoperability without third-party bindings
  • class-file inspection without external bytecode libraries
  • current Java language/API features that are useful in interviews

That makes them good interview material. They let you explain not only what changed in Java, but also why the change exists and how it can be tested in a small project.