Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/jabrena/cursor-rules-examples/142-java-functional-programmingnpx skills add jabrena/cursor-rules-examples --skill 142-java-functional-programminggit clone --depth 1 https://github.com/jabrena/cursor-rules-examplesWhat it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00096 | $0.00645 |
| Opus 5 | $0.00048 | $0.00322 |
| Sonnet 5 | $0.00019 | $0.00129 |
| Haiku 4.5 | $0.00010 | $0.00064 |
Grade A, and why
142-java-functional-programming scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 49 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Java Functional Programming rules
Identify and apply functional programming principles in Java to improve immutability, expressiveness, and maintainability.
What is covered in this Skill?
- Immutable objects and Records (JEP 395)
- Pure functions free of side effects
- Functional interfaces:
Function,Predicate,Consumer,Supplier, custom@FunctionalInterface - Lambda expressions and method references
- Stream API: filter/map/reduce pipelines, parallel streams,
toUnmodifiable*collectors Optionalidiomatic usage:map/flatMap/filter/orElse*overisPresent()+get()- Function composition:
andThen/compose - Higher-order functions: memoization, currying, partial application
- Pattern Matching for
instanceofandswitch(Java 21) - Sealed classes and interfaces (Java 17) for exhaustive domain hierarchies
- Switch Expressions (Java 14), Stream Gatherers (JEP 461)
- Effect-boundary separation: side effects at edges, pure core logic
- Immutable collections:
List.of(),Collectors.toUnmodifiableList()
Scope: The reference is organized by examples (good/bad code patterns) for each core area. Apply recommendations based on applicable examples.
Constraints
Before applying any functional programming changes, ensure the project compiles. If compilation fails, stop immediately — do not proceed until the project compiles successfully. Verify that maven-compiler-plugin source/target supports the Java features being used.
- MANDATORY: Run
./mvnw compileormvn compilebefore applying any changes - SAFETY: If compilation fails, stop immediately — do not proceed until the project compiles successfully
- VERIFY: Verify maven-compiler-plugin source/target supports the Java features being used
- VERIFY: Run
./mvnw clean verifyormvn clean verifyafter applying improvements - BEFORE APPLYING: Read the reference for detailed good/bad examples, constraints, and safeguards for each functional programming pattern
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- yesterday First seen · 49 lines · 96 tokens per session scan A 2de2cb9aab3c
142-java-functional-programming is a skill published in the GitHub repository jabrena/cursor-rules-examples (2 stars, last pushed 5d ago), licensed Apache-2.0. It adds 96 tokens to every session and 645 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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