Java Design Patterns Reference
decebals/claude-code-java
A practical Java reference for Builder, Factory, Singleton, Strategy, Observer and other patterns, with a table matching problems to patterns.
A skill your agent uses when you need to apply functional programming principles in Java — including writing immutable objects and Records, pure functions, functional interfaces, lambda expressions…
Install 142 Java Functional Programming
$ npx skills add jabrena/plinth --skill 142-java-functional-programming -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install jabrena/plinth 142-java-functional-programming --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/jabrena/plinth.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/142-java-functional-programming .claude/skills/142-java-functional-programming && rm -rf skills-srcUse ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.
Claude Code skills documentation · loads skills from .claude/skills/
Install the "142-java-functional-programming" agent skill from https://github.com/jabrena/plinth/tree/main/skills/142-java-functional-programming into .claude/skills/142-java-functional-programming/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "142-java-functional-programming", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/jabrena/plinth/tree/main/skills/142-java-functional-programmingType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add jabrena/plinth --skill 142-java-functional-programming -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install jabrena/plinth 142-java-functional-programming --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/jabrena/plinth.git skills-src && mkdir -p .agents/skills && cp -r skills-src/skills/142-java-functional-programming .agents/skills/142-java-functional-programming && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "142-java-functional-programming" agent skill from https://github.com/jabrena/plinth/tree/main/skills/142-java-functional-programming into .agents/skills/142-java-functional-programming/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "142-java-functional-programming", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add jabrena/plinth --skill 142-java-functional-programming -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install jabrena/plinth 142-java-functional-programming --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/jabrena/plinth.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/skills/142-java-functional-programming .cursor/skills/142-java-functional-programming && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "142-java-functional-programming" agent skill from https://github.com/jabrena/plinth/tree/main/skills/142-java-functional-programming into .cursor/skills/142-java-functional-programming/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "142-java-functional-programming", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/jabrena/plinth.git --path skills/142-java-functional-programming--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add jabrena/plinth --skill 142-java-functional-programming -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install jabrena/plinth 142-java-functional-programming --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/jabrena/plinth.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/skills/142-java-functional-programming .gemini/skills/142-java-functional-programming && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "142-java-functional-programming" agent skill from https://github.com/jabrena/plinth/tree/main/skills/142-java-functional-programming into .gemini/skills/142-java-functional-programming/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "142-java-functional-programming", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install jabrena/plinth 142-java-functional-programmingInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add jabrena/plinth --skill 142-java-functional-programming -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/jabrena/plinth.git skills-src && mkdir -p .github/skills && cp -r skills-src/skills/142-java-functional-programming .github/skills/142-java-functional-programming && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "142-java-functional-programming" agent skill from https://github.com/jabrena/plinth/tree/main/skills/142-java-functional-programming into .github/skills/142-java-functional-programming/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "142-java-functional-programming", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add jabrena/plinth --skill 142-java-functional-programming -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install jabrena/plinth 142-java-functional-programming --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/jabrena/plinth.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/skills/142-java-functional-programming .opencode/skills/142-java-functional-programming && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "142-java-functional-programming" agent skill from https://github.com/jabrena/plinth/tree/main/skills/142-java-functional-programming into .opencode/skills/142-java-functional-programming/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "142-java-functional-programming", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
142-java-functional-programming- GitHub stars
- 446
- Token cost
- ~1.1k tokens
- SKILL.md length
- 396 words
- Files
- 2 (incl. references)
- Skills in repo
- 124
- Repo updated
- First seen
- Licence
- Apache-2.0
At a glance
A skill your agent uses when you need to apply functional programming principles in Java — including writing immutable objects and Records, pure functions, functional interfaces, lambda expressions…
- You need to apply functional programming principles in Java — including writing immutable objects and Records
- SKILL.md covers Constraints, When to use this skill, Workflow and Reference
- Calls mvn
- Functional interfaces
What it does
142 Java Functional Programming is an agent skill from jabrena/plinth. 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…
Its SKILL.md is about 1.1k tokens, which your agent loads only when the skill is triggered. The skill folder holds 2 other files, including reference files (for example `references/142-java-functional-programming.md`).
It sits in Development, covering Refactoring. It works with Java. The repository describes itself as: Plinth is an AI-native engineering toolkit for modern Java enterprise SDLC, built around reusable Commands, Agents, Skills, and MCP Servers. The licence is Apache-2.0.
When your agent uses it
- You need to apply functional programming principles in Java — including writing immutable objects and Records
- Functional interfaces
- Lambda expressions
- Stream API pipelines
Example prompts
- “/142-java-functional-programming”
What it can do on your machine
Read from SKILL.md and the folder at commit dca88dc. It shows what the files ask for, not the result of running them.
Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
Shell commands in SKILL.md call:
mvn
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.
Context cost
142 Java Functional Programming loads about 1.1k tokens when it runs, and up to ~12k if it reads all its reference files. Until then it costs about 208 tokens; SKILL.md has 396 words of instructions outside code blocks.
Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.
Safety
Auto-check passed
The automated check found no risky patterns in SKILL.md.
Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.
SKILL.md
The full file from jabrena/plinth at commit dca88dc, republished under its Apache-2.0 licence (© jabrena). 396 words, ~1,090 tokens.
Download SKILL.mdSave it as
.claude/skills/142-java-functional-programming/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.- name
- 142-java-functional-programming
- description
- 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
- license
- Apache-2.0
- metadata.author
- Juan Antonio Breña Moral
- metadata.version
- 0.19.0
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
- 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
Show full SKILL.md (129 more words)Show less
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.
© jabrena, Apache-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file
Files
SKILL.md and 1 other file (references) in skills/142-java-functional-programming of jabrena/plinth.
- SKILL.md
- references/142-java-functional-programming.md
Open the folder on GitHubat commit dca88dc
Compare with similar skills
142 Java Functional Programming next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| 142 Java Functional Programming this skilljabrena/plinth | 446 | — | ~1.1k | Automated safety check: Pass | Apache-2.0 | |
| Java Design Patterns Referencedecebals/claude-code-java | 751 | 1 repos | ~4.4k | Automated safety check: Pass | MIT | |
| Bootui Java Developmentjdubois/boot-ui | 307 | — | ~1.3k | Automated safety check: Pass | Apache-2.0 | |
| Goinference-gateway/inference-gateway | 214 | — | ~2.4k | Automated safety check: Pass | Apache-2.0 | |
| Java 21 Developer Guide for Grailsapache/grails-core | 2.9k | — | ~1.9k | Automated safety check: Pass | Apache-2.0 | |
| Spring Data Developmentarangodb/spring-data | 116 | — | ~620 | Automated safety check: Pass | Apache-2.0 |
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Questions about 142 Java Functional Programming
What does 142 Java Functional Programming do?
A skill your agent uses when you need to apply functional programming principles in Java — including writing immutable objects and Records, pure functions, functional interfaces, lambda expressions…. 142 Java Functional Programming is an agent skill from jabrena/plinth. 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.
When should I use 142 Java Functional Programming?
142 Java Functional Programming fits situations like: you need to apply functional programming principles in Java — including writing immutable objects and Records; functional interfaces; lambda expressions; stream API pipelines.
How do I install 142 Java Functional Programming in Claude Code?
Run `npx skills add jabrena/plinth --skill 142-java-functional-programming -a claude-code`. Or copy the skill folder (skills/142-java-functional-programming in jabrena/plinth) into .claude/skills/142-java-functional-programming in your project. Claude Code loads it when a task matches its description.
How do I install 142 Java Functional Programming in Codex?
Run `npx skills add jabrena/plinth --skill 142-java-functional-programming -a codex`. Or copy the skill folder (skills/142-java-functional-programming in jabrena/plinth) into .agents/skills/142-java-functional-programming in your project. Codex loads it when a task matches its description.
Can I use 142 Java Functional Programming in Cursor, Gemini CLI or GitHub Copilot?
Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add jabrena/plinth --skill 142-java-functional-programming -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/142-java-functional-programming, .gemini/skills/142-java-functional-programming, .github/skills/142-java-functional-programming and .opencode/skills/142-java-functional-programming in your project.
What does 142 Java Functional Programming need to run?
Going by SKILL.md and its folder, 142 Java Functional Programming needs the command-line tools its instructions call (mvn).
Does 142 Java Functional Programming access the network?
SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.
Is 142 Java Functional Programming safe to install?
Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.
What licence does 142 Java Functional Programming use?
142 Java Functional Programming is published under the Apache-2.0 licence (declared in SKILL.md). It allows redistribution, so the full SKILL.md is shown on this page.
How many tokens does 142 Java Functional Programming use?
About 1.1k tokens (SKILL.md is roughly 4.4k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 11k tokens, read only when the agent opens those files.
What are the alternatives to 142 Java Functional Programming?
Skills that share tags, products or a category with 142 Java Functional Programming: Java Design Patterns Reference (decebals/claude-code-java, 751 stars), Bootui Java Development (jdubois/boot-ui, 307 stars), Go (inference-gateway/inference-gateway, 214 stars) and Java 21 Developer Guide for Grails (apache/grails-core, 2.9k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains 142 Java Functional Programming?
jabrena (a GitHub user) maintains it in jabrena/plinth, which has 446 GitHub stars. The repository holds 124 skills in this directory. The repository was last updated on October 7, 2026.
Source: jabrena/plinth on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.