12 parts · 14 chapters

Java, with Spring Boot and Quarkus

Java runs most of the world's banks, payment processors and large enterprises, and modern Java is a different language from the one many people remember: records, sealed types, pattern matching and virtual threads. Measured here on Java 26: 100,000 virtual threads each sleeping one second finished in 1.49 s.

Twelve parts in the shared shape, with an extra for Quarkus: basics; the type system; the JVM (class loading, JIT, GC); concurrency and virtual threads; idioms; tooling and testing; Spring Boot end to end; Spring internals; Quarkus and GraalVM native images; performance; what Java is paired with in production, including Spring Cloud and sidecars (Envoy, Istio, Dapr); and the ledger API capstone.

Start reading · Part 0 Present as slides
basics · the type system · the JVM · concurrency and virtual threads · idioms · tooling and testing · Spring Boot end to end · Spring internals · Quarkus and native images · performance · in production with sidecars · capstonebeginner → expert · engineers joining JVM-based banks, fintechs and enterprises
modern JavaRecords, sealed interfaces, pattern matching, var, text blocks, streams.
the JVMClass loading, bytecode, tiered JIT, G1, ZGC, and tuning.
virtual threadsLoom: millions of cheap threads, measured here.
Spring BootDI, auto-configuration, Data JPA, Security, WebFlux.
QuarkusBuild-time DI and GraalVM native images for fast startup.
productionSpring Cloud, Kafka, sidecars with Envoy, Istio and Dapr.
00

Basics

From 1996 to modern Java · Projects, collections and exceptions
2 ch · ~12 min01

The Type System

Records, sealed types and patterns
1 ch · ~8 min02

The JVM

Class loading, JIT and GC
1 ch · ~8 min03

Concurrency and Virtual Threads

From thread pools to virtual threads · java.util.concurrent and structured concurrency
2 ch · ~12 min04

Idioms

Writing modern Java
1 ch · ~8 min05

Tooling and Testing

Build and test
1 ch · ~8 min06

Spring Boot End to End

A Spring Boot service
1 ch · ~8 min07

Spring Internals

Wiring and proxies
1 ch · ~8 min08

Quarkus and Native Images

Quarkus in practice
1 ch · ~8 min09

Performance and Profiling

Measuring the JVM
1 ch · ~8 min10

In Production: Spring Cloud and Sidecars

Libraries or sidecars
1 ch · ~8 min11

Capstone: The Ledger API in Java

The build
1 ch · ~8 min
Language courses share one shapeSame parts and ledger capstone as Go, Python, Rust and Rails. Service Mesh (course 12) covers sidecars in depth; ORM Internals covers Hibernate.