feat: implement Immutable pattern (Fixes #3448)

[alex052525]

Pull Request Template

What does this PR do?

Adds the Immutable design pattern module, which was missing from the repository.

• Fixes Missing Pattern Immutable #3448

Implementation highlights

• ImmutableUser — final class with final fields, defensive copy via List.copyOf(),
  and wither methods (withName, withAge, withRoles) that return new instances instead of mutating state
• App — runnable demo showing immutability and defensive copy in action
• ImmutableUserTest — 10 JUnit 5 tests covering construction, wither behaviour,
  original-object invariance, defensive copy, and unmodifiable getter
• etc/immutable.urm.puml — PlantUML class diagram
• README.md — full pattern documentation following project conventions

[github-actions]

PR Summary

Introduces a new immutable module implementing the Immutable design pattern. Adds an ImmutableUser final class with final fields, defensive copy for lists, and wither methods (withName, withAge, withRoles). Includes a runnable App demo, JUnit 5 tests, PlantUML diagram, and README docs. Updates root pom to include the new module. Fixes #3448.

Changes

File	Summary
immutable/README.md	Adds documentation for the Immutable design pattern, including a complete Java example (ImmutableUser), a runnable App demo, defensive-copy semantics, and references.
immutable/etc/immutable.urm.puml	PlantUML diagram for the Immutable module showing App and ImmutableUser with their relationships and wither usage.
immutable/pom.xml	New Maven module for immutable with dependencies (SLF4J, Logback, JUnit 5), build plugin for executable JAR, and main class configuration.
immutable/src/main/java/com/iluwatar/immutable/App.java	Demo app that constructs an ImmutableUser, demonstrates the withAge wither, and shows defensive copy behavior of roles.
immutable/src/main/java/com/iluwatar/immutable/ImmutableUser.java	Defines ImmutableUser as a final class with final fields; defensively copies roles via List.copyOf; provides withName, withAge, withRoles methods returning new instances; includes toString.
immutable/src/test/java/com/iluwatar/immutable/ImmutableUserTest.java	JUnit 5 tests covering constructor, withers, immutability invariants, defensive copy, and unmodifiable getRoles behavior.
pom.xml	Updated root POM to declare the new immutable module in the build.

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autogenerated by presubmit.ai

[github-actions]

🚨 Pull request needs attention.

Review Summary

Commits Considered (2)

• bc9f946: feat: add withName and withRoles wither methods to ImmutableUser #3448

Every field now has a corresponding wither for consistency.

Co-Authored-By: Claude Sonnet 4.6 noreply@anthropic.com

• 481543b: feat: implement Immutable pattern #3448

Add immutable/ module with ImmutableUser (final class, defensive copy,
withAge wither method), App demo, JUnit 5 tests, PlantUML diagram, and
README following project conventions.

Co-Authored-By: Claude Sonnet 4.6 noreply@anthropic.com

Files Processed (7)

• immutable/README.md (1 hunk)
• immutable/etc/immutable.urm.puml (1 hunk)
• immutable/pom.xml (1 hunk)
• immutable/src/main/java/com/iluwatar/immutable/App.java (1 hunk)
• immutable/src/main/java/com/iluwatar/immutable/ImmutableUser.java (1 hunk)
• immutable/src/test/java/com/iluwatar/immutable/ImmutableUserTest.java (1 hunk)
• pom.xml (1 hunk)

Actionable Comments (1)

• immutable/pom.xml [46-49]

  maintainability: "Add JUnit Jupiter API as a test dependency"

Skipped Comments (0)

[github-actions]

JUnit Jupiter API dependency is missing. Tests in this module rely on org.junit.jupiter.api APIs (e.g., assertThrows, @test). Add junit-jupiter-api as a test dependency to ensure the test compilation succeeds alongside junit-jupiter-engine.