Add Featureflip Java SDK

[jhoward321]

Adds the Featureflip Java SDK to Feature Flags in README_SOURCE.md.

Disclosure: I work on Featureflip. Per CONTRIBUTING, self-promotion is welcome when the project meets the same criteria — happy to be held to that bar.

Against the stated criteria

• Java as a primary API / first-class integration — yes. Published to Maven Central as io.featureflip:featureflip-java, currently 2.9.0.
• Fills a useful niche — it evaluates flags in-process rather than calling out per evaluation, with configuration streamed over server-sent events, so evaluation stays local and updates arrive without polling.
• English documentation and clear licensing — Apache-2.0, docs at https://featureflip.io/docs/sdks/java/
• Clear pricing and a free tier when commercial — pricing is public at https://featureflip.io/pricing/ with no signup wall, and the free Solo plan does not expire (1 project, 10 flags, 2 environments, no card).

Notes on the entry

• Edited README_SOURCE.md only — the generated README.md is untouched, and I have not run the generator.
• Placed alphabetically before FF4J.
• Linked the canonical GitHub repository rather than the website.
• No license or commercial badge added manually; the description is deliberately worded to be distinctive from the neighbouring Unleash and Rollgate SDK entries rather than restating them.
• One pull request, one project.

🤖 Generated with Claude Code

https://claude.ai/code/session_01DFrAfK9aLuTuYw9Qo6XwsU

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Summary by cubic

Adds the Featureflip Java SDK to the Feature Flags list in README_SOURCE.md, placing it before FF4J. The SDK evaluates flags in-process with configuration streamed over server-sent events. The generated README.md is left untouched.

^{Written for commit 4e99042. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 1 file

_{Re-trigger cubic}