The Java Realization / JBCT course

Java Backend Coding Technology — Course

Twenty-two lessons across six parts. Each pairs the book’s prose with a short exercise; progress is tracked locally in your browser, no account required.

Part I — Foundations

4 lessons

1Introduction - Code Unification
Why JBCT exists, the problems it fixes, and how the rest of the course is organized.
2From Process to Patterns
How a business process becomes a data dependency graph, and why pattern choice follows from it.
3The Four Return Types
The four return types - T, Option, Result, Promise - and the decision rule for choosing between them.
4Pragmatica Core Essentials
Installing Pragmatica Core and its shared vocabulary: map, flatMap, filter, and recover across all four types.

Part II — The Type Discipline

3 lessons

1Parse, Don't Validate
Make invalid states unrepresentable: validation becomes construction, not a separate step.
2Error Handling & Composition
Errors as typed Cause values instead of exceptions, with exhaustive switches and clean composition.
3Null Policy & Error Recovery
When null is acceptable, converting it to Option at the boundary, and the recovery triple.

Part III — Patterns

4 lessons

1Basic Patterns & Structure
The three basic patterns - Leaf, Condition, Iteration - and mechanical rules for extracting functions.
2Advanced Patterns
Sequencer, Fork-Join, and Aspects - composing basic patterns into real workflows.
3Knowledge-Gathering Pipelines
Growing context between pipeline steps, and the mapWith family that keeps each stage to one line.
4Thread Safety
Why immutability makes JBCT code thread-safe by default, pattern by pattern.

Part IV — Testing

2 lessons

1Testing Philosophy
Integration-first testing: stub everything, then implement incrementally toward production-ready.
2Testing in Practice
Organizing large test suites, what to test where, and migrating from traditional unit tests.

Part V — Worked Examples

4 lessons

1Complete Example - RegisterUser
A complete use case, RegisterUser, built step by step from requirements to production code.
2Complete Example - PlaceOrder
Fork-Join for parallel inventory checks, Sequencer for the payment flow, and compensation on failure.
3Focused Example - PublishArticle
The Condition pattern in a real workflow: routing an article's approval path by author tier.
4Focused Example - TransferFunds
Aspects in a real workflow: retry, timeout, and audit logging composed around a funds transfer.

Part VI — In Production

5 lessons

1Project Structure & Framework Integration
Vertical slicing, the telescope rule for package growth, and where each type belongs.
2Systematic Application Guide
Eight checkpoints for applying JBCT consistently, in new code and in review.
3Migration Strategies
A phased playbook for adopting JBCT in an existing codebase without a big-bang rewrite.
4Comparison with Other Approaches
Where JBCT fits against layered, hexagonal, and clean architecture, and what it borrows or rejects.
5Troubleshooting & FAQ
Debugging monadic chains, common mistakes, and quick answers to the questions that come up most.