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Java Learning Module Implementation Plan

Summary

Create a lightweight, module-based Java learning project in /Users/mirzaaziz/workspace/java-learning-module, modeled after the Python reference project’s structure:

README.md
modules/<module-name>/{01-objectives,02-concepts,03-exercises,04-verification}

The course targets backend engineers with basic Java knowledge and takes them from practical core Java through enterprise backend readiness. Runnable hands-on work focuses on Java and Spring Boot. Android and Big Data are included as transfer/application modules without requiring Android SDK, Hadoop, Spark clusters, or heavy local setup.

Defaults chosen:

  • Java baseline: Java 17 LTS
  • Build tool: Gradle Wrapper
  • Domain: e-commerce orders
  • Exercise format: starter code plus solution files
  • Scope: 13 modules (00–12)

Key Changes

  • Add root project documentation:

    • README.md — course map, prerequisites, setup, module order, expected outcomes
    • BACKGROUND.md — why Java matters for backend, Android, enterprise systems, and data platforms
    • CLAUDE.md — contributor guidance for maintaining the learning module style
    • .gitignore — Gradle, IDE, build, and OS artifacts

  • Add a root Gradle build:

    • settings.gradle.kts
    • build.gradle.kts
    • gradlew, gradlew.bat, gradle/wrapper/*
    • Use Java 17 toolchain
    • Use JUnit 5 for runnable exercises
    • Use Spring Boot only in Spring modules
    • Avoid a global Gradle dependency (local system Gradle currently fails); learners use ./gradlew

  • Use the same learning structure for each module:

    • 01-objectives/README.md
    • 02-concepts/*.md
    • 03-exercises/*.md
    • Runnable starter code under src/main/java or src/test/java where useful
    • Solution code under solutions/
    • 04-verification/checklist.md

Module Plan

  1. 00-setup-java-gradle

    • Install/verify JDK 17, explain JVM/JDK/JRE, run ./gradlew test
    • Explain Gradle wrapper, project layout, and IDE import

  2. 01-java-refresh-oop

    • Classes, records, interfaces, enums, packages, access modifiers
    • Exercise: model Product, Customer, Order, and OrderStatus

  3. 02-collections-generics-optionals

    • Lists, maps, sets, generics, Optional, equality, immutability basics
    • Exercise: calculate order totals and group orders by customer/status

  4. 03-functional-java-streams

    • Lambdas, method references, streams, collectors, predicates
    • Exercise: filter, aggregate, and summarize e-commerce orders

  5. 04-exceptions-validation-testing

    • Checked vs unchecked exceptions, validation boundaries, JUnit 5, assertions
    • Exercise: validate order placement rules with unit tests

  6. 05-concurrency-and-jvm-basics

    • Threads, executors, futures, synchronization risks, JVM memory basics
    • Exercise: process order notifications concurrently with deterministic tests

  7. 06-spring-boot-rest-api

    • Controllers, services, DTOs, dependency injection, request/response flow
    • Exercise: build CRUD-style order endpoints

  8. 07-persistence-hibernate-jpa

    • Entities, repositories, transactions, lazy loading, schema basics
    • Exercise: persist orders with Spring Data JPA and H2

  9. 08-enterprise-api-quality

    • Validation, error handling, pagination, configuration, logging
    • Exercise: add request validation, structured errors, and pageable order search

  10. 09-security-observability-production

    • Authentication concepts, Spring Security basics, actuator, health checks, metrics
    • Exercise: protect write endpoints and expose operational health

  11. 10-android-java-orientation

    • How Java maps to Android app architecture, activities/services at a high level, constraints vs backend Java
    • Exercise: design-only walkthrough for consuming the order API from an Android client; no Android SDK required

  12. 11-big-data-java-orientation

    • JVM role in Hadoop/Spark ecosystems, batch vs streaming concepts, serialization, partitioning
    • Exercise: local Java-only analytics simulation over order events; explain how it maps to Spark jobs

  13. 12-capstone-enterprise-orders

    • Consolidate prior modules into a small Spring Boot order service
    • Includes REST API, validation, persistence, tests, basic security, health checks, and analytics-style reporting

Public Interfaces And Project Shape

  • Root commands:

    • ./gradlew test
    • ./gradlew :modules:06-spring-boot-rest-api:test
    • ./gradlew :modules:12-capstone-enterprise-orders:bootRun

  • Package naming:

    • com.learning.java.core
    • com.learning.java.orders
    • com.learning.java.orders.api
    • com.learning.java.orders.domain
    • com.learning.java.orders.persistence
    • com.learning.java.orders.service

  • Core domain types:

    • Product
    • Customer
    • Order
    • OrderItem
    • OrderStatus
    • Money
    • OrderService
    • OrderRepository

  • Spring API shape:

    • GET /orders
    • GET /orders/{id}
    • POST /orders
    • PATCH /orders/{id}/status
    • GET /actuator/health

  • Keep examples intentionally small:

    • In-memory repositories in early modules
    • H2 database for persistence modules
    • No Docker requirement in v1
    • No real payment, real auth provider, Android SDK, Hadoop, or Spark runtime

Test Plan

  • Root verification:

    • ./gradlew test passes for all runnable modules
    • Each module checklist includes exact commands and expected success signals

  • Unit tests:

    • Domain modeling, collection operations, stream aggregations, validation, exception behavior, and concurrency behavior

  • Spring tests:

    • Controller tests for HTTP status and JSON shape
    • Service tests for order placement/status transitions
    • Repository tests for JPA persistence
    • Security tests for protected write endpoints

  • Documentation checks:

    • README navigation links resolve to real module paths

Version Decisions

  • Java 17 is selected because it is installed locally and remains a Spring Boot-compatible enterprise baseline.
  • Newer Java 21/25 features can be mentioned in advanced notes, but runnable code stays on Java 17.
  • Spring Boot version should be pinned during implementation to a current supported version compatible with Java 17. Official Spring docs currently state Spring Boot 4.1 requires Java 17+ and supports Java 26, while Spring Boot 3.x also uses Java 17 as a baseline.
  • Gradle toolchains and the Gradle Wrapper will be used for reproducible builds, following Gradle’s official guidance.

References: