142-java-functional-programming

Q: How do I install 142-java-functional-programming?

Run npx skills add https://github.com/jabrena/plinth --skill 142-java-functional-programming in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/142-java-functional-programming/ (personal) or .claude/skills/142-java-functional-programming/ (project).

by jabrenaBackend & APIs

Use when you need to apply functional programming principles in Java — including writing immutable objects and Records, pure functions, functional interfaces, lambda expressions, Stream API pipelines, Optional for null safety, function composition, higher-order functions, pattern matching for instanceof and switch, sealed classes/interfaces for controlled hierarchies, Stream Gatherers for custom operations, currying/partial application, effect boundary separation, and concurrent-safe functional patterns. This should trigger for requests such as Improve the code with Functional Programming; Apply Functional Programming; Refactor the code with Functional Programming; Refactor Java code to use streams or Optionals safely; Improve immutability and pure functions in Java. Part of Plinth Toolkit

Installs: 379
Last 24h: —
Trending rank: —
Security: Not audited

Install

Works with every agent the skills CLI supports.

npx skills add https://github.com/jabrena/plinth --skill 142-java-functional-programming

01
Install
Run the command in your project. The CLI asks which agents to install for.
02
Describe the task
Ask your agent for something this skill covers. It loads 142-java-functional-programming automatically when relevant.
03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.

SKILL.md

The instructions your agent reads when the skill is triggered.

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
Optional idiomatic usage: map/flatMap/filter/orElse* over isPresent()+get()
Function composition: andThen/compose
Higher-order functions: memoization, currying, partial application
Pattern Matching for instanceof and switch (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 compile or mvn compile before 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 verify or mvn clean verify after applying improvements
BEFORE APPLYING: Read the reference for detailed good/bad examples, constraints, and safeguards for each functional programming pattern
EDGE CASE: If request scope is ambiguous, stop and ask a clarifying question before applying changes
EDGE CASE: If required inputs, files, or tooling are missing, report what is missing and ask whether to proceed with setup guidance

When to use this skill

Improve the code with Functional Programming
Apply Functional Programming
Refactor the code with Functional Programming
Refactor Java code to use streams or Optionals safely
Improve immutability and pure functions in Java

Workflow

Compile project before functional refactoring

Run ./mvnw compile or mvn compile and stop immediately if compilation fails.

Confirm Java feature compatibility

Verify maven-compiler-plugin source/target supports the functional features planned for adoption.

Read functional-programming reference and assess code

Read references/142-java-functional-programming.md and identify opportunities for immutability, pure functions, and functional composition.

Apply functional programming improvements

Implement selected functional refactorings while keeping side effects at boundaries.

Verify with full build

Run ./mvnw clean verify or mvn clean verify after applying improvements.

Reference

For detailed guidance, examples, and constraints, see references/142-java-functional-programming.md.

FAQ

What does the 142-java-functional-programming skill do?

How do I install 142-java-functional-programming?

Run npx skills add https://github.com/jabrena/plinth --skill 142-java-functional-programming in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/142-java-functional-programming/ (personal) or .claude/skills/142-java-functional-programming/ (project).

Which AI agents can use 142-java-functional-programming?

Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.

Is 142-java-functional-programming safe to install?

No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.

Who maintains 142-java-functional-programming?

It is published by jabrena in jabrena/plinth. It has 379 recorded installs.

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