# Description of Changes
Please provide a summary of the changes, including:
- **What was changed**
Added the `final` modifier to the `ReplaceAndInvertColorService` field
in `ReplaceAndInvertColorController` and to the
`ReplaceAndInvertColorFactory` field in `ReplaceAndInvertColorService`.
This ensures that Lombok’s `@RequiredArgsConstructor` generates
constructors for these dependencies, enabling proper constructor-based
injection instead of leaving them null.
- **Why the change was made**
Without the `final` keyword, Lombok does not include non-final fields in
the generated constructor, causing Spring to leave them uninitialized
and resulting in a `NullPointerException` during runtime when invoking
`replaceAndInvert` on the factory/service.
---
## Checklist
### General
- [x] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [x] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/HowToAddNewLanguage.md)
(if applicable)
- [x] I have performed a self-review of my own code
- [x] My changes generate no new warnings
### Documentation
- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)
### UI Changes (if applicable)
- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)
### Testing (if applicable)
- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md#6-testing)
for more details.
