Summary

# Java summary

You can now:

- Author modern Java with records, sealed types, pattern matching, text blocks
- Use streams + collectors + Optional fluently
- Apply virtual threads + structured concurrency for IO
- Build Spring Boot 3 services with minimal starters
- Persist with Spring Data JPA + Postgres + Testcontainers
- Observe with Micrometer + OpenTelemetry
- Containerise with multi-stage builds; non-root, pinned base
- Ship with GitHub Actions + OIDC

# Your next step - virtual threads + structured concurrency

import java.util.concurrent.StructuredTaskScope;
import java.net.http.*;
import java.net.URI;

record Page(String url, String body) {}

public class Fetcher {
  public static void main(String[] args) throws Exception {
    try (var scope = new StructuredTaskScope.ShutdownOnFailure()) {
      var a = scope.fork(() -> get('https://example.com/'));
      var b = scope.fork(() -> get('https://example.org/'));
      scope.join();
      scope.throwIfFailed();
      System.out.println(a.get().body().length() + b.get().body().length());
    }
  }
  static Page get(String url) throws Exception {
    var http = HttpClient.newHttpClient();
    var req  = HttpRequest.newBuilder(URI.create(url)).build();
    var res  = http.send(req, HttpResponse.BodyHandlers.ofString());
    return new Page(url, res.body());
  }
}

// Next: Spring Boot deep dive, virtual threads, GraalVM native images.