java.evolved

Java has evolved. Your code can too.

A collection of side-by-side code comparisons showing old Java patterns next to their clean, modern replacements — from Java 8 all the way to Java 25.

🔗 javaevolved.github.io

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What is this?

Every snippet shows two panels:

• ✕ Old — the traditional way (Java 7/8 era)
• ✓ Modern — the clean, idiomatic replacement (Java 9–25)

Each comparison includes an explanation of why the modern approach is better, which JDK version introduced it, and links to related patterns.

Categories

Category	Examples
Language	Records, sealed classes, pattern matching, switch expressions, var, unnamed variables
Collections	Immutable factories, sequenced collections, unmodifiable collectors
Strings	Text blocks, isBlank(), strip(), repeat(), formatted(), indent()
Streams	toList(), mapMulti(), takeWhile()/dropWhile(), gatherers
Concurrency	Virtual threads, structured concurrency, scoped values, ExecutorService as AutoCloseable
I/O	Files.readString(), writeString(), Path.of(), transferTo(), HTTP Client
Errors	requireNonNullElse(), record-based errors, deserialization filters
Date/Time	java.time basics, Duration/Period, DateTimeFormatter, instant precision
Security	TLS defaults, SecureRandom, PEM encoding, key derivation functions
Tooling	JShell, single-file execution, JFR profiling, compact source files, AOT

Architecture

This site uses a JSON-first build pipeline:

• Source of truth: Individual content/category/slug.json files (85 across 10 category folders)
• Templates: templates/ — shared HTML templates with {{placeholder}} tokens
• Generator: html-generators/generate.jar — pre-built fat JAR that produces all HTML detail pages and data/snippets.json
• Deploy: GitHub Actions runs the generator and deploys to GitHub Pages

Generated files (site/category/*.html and site/data/snippets.json) are in .gitignore — never edit them directly.

Build & run locally

Prerequisites

• Java 25+ (e.g. Temurin)

Generate and serve

# Generate all HTML pages and data/snippets.json into site/
java -jar html-generators/generate.jar

# Serve locally
jwebserver -b 0.0.0.0 -d site -p 8090
# Open http://localhost:8090

The fat JAR is a self-contained ~2.2 MB file with all dependencies bundled. No JBang installation needed.

For development on the generator itself, you can use JBang or Python — see html-generators/README.md for details.

Contributing

Contributions are welcome! Content is managed as JSON files — never edit generated HTML.

1. Fork the repo
2. Create or edit a JSON file in the appropriate content folder (e.g. content/language/my-feature.json)
3. Follow the snippet JSON schema for all required fields
4. Run java -jar html-generators/generate.jar to verify your changes build correctly
5. Update site/index.html with a new preview card if adding a new snippet
6. Open a pull request

Please ensure JDK version labels only reference the version where a feature became final (non-preview).

Tech stack

• Plain HTML, CSS, and JavaScript — no frontend frameworks
• JBang + Jackson for build-time generation
• Hosted on GitHub Pages via GitHub Actions

Author

Bruno Borges

• GitHub: @brunoborges
• X/Twitter: @brunoborges
• LinkedIn: brunocborges

License

This project is licensed under the MIT License.