142-java-functional-programming SKILL.md skillA

142-java-functional-programming from jabrena/plinth is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.

Install it, pinned
mdr add jabrena/plinth/142-java-functional-programming@v0.19.0

Pins v0.19.0 in mdr.lock. Pin the fingerprint instead.

Audit grade
A, 17 of 17 checks passed
Kind
SKILL.md skill
Repository
jabrena/plinth
Path
skills/142-java-functional-programming/SKILL.md
Versions recorded
6
Latest version
v0.19.0, committed Sep 26, 2026
First version recorded
Apr 26, 2026
Size
4,366 bytes
Repository stars
461
License
Apache-2.0

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…

Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.

What the file says

# 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()`
…

Read the whole file at its exact version.

How to install

The exact contents, by fingerprint
mdr add jabrena/plinth/142-java-functional-programming@sha256:8c0eada2d90c63cf

The line at the top of this page pins the label v0.19.0, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.

Badge

mdr badge

[![mdr](https://markdownregistry.com/badge/art_xe42d7ekrc63q4fa.svg)](https://markdownregistry.com/a/art_xe42d7ekrc63q4fa)

4 badge image fetches in 30 days. What the badge shows.

Versions

The registry has recorded 6 versions of this file, between Apr 26, 2026 and Sep 26, 2026, about one every 31 days.

versioncommittedcommitsizeaudit
v0.19.0 latest2026-09-26 9569c35 4,366 BA view · diff
v0.18.02026-08-01 26b0e71 4,366 BA view · diff
v0.17.02026-07-10 aaee915 4,366 BA view · diff
v0.16.02026-06-15 b73c9d3 4,167 BA view · diff
v0.15.02026-05-29 a800339 4,167 BA view · diff
v0.15.0-SNAPSHOT2026-04-26 819f349 4,176 BA view

Audit of the latest version

A  17 of 17 checks passed. Fixed automatic checks with no AI involved, so the same checks give the same answer every run.
  • pass: Frontmatter block present
  • pass: Frontmatter declares a name
  • pass: Frontmatter declares a description
  • pass: Size between 200 bytes and 200 KB (4366 bytes)
  • pass: No zero-width or bidi control characters
  • pass: No instruction hidden inside an HTML comment
  • pass: No link to an exfiltration or paste host
  • pass: No credential-shaped string
  • pass: No instruction to send local credentials anywhere
  • pass: No text hidden with inline styles
  • pass: No prompt-injection phrasing
  • pass: No curl or wget piped into a shell
  • pass: No recursive delete of root, home or parent
  • pass: No instruction to read or print local credentials
  • pass: No base64 blob over 200 characters
  • pass: No link to a raw IP address
  • pass: No script tag

Source

GitHub

jabrena/plinth · 461 stars · license Apache-2.0 · pushed 2026-11-06 · branch main

API

GET https://markdownregistry.com/api/v1/artifacts/art_xe42d7ekrc63q4fa
GET https://markdownregistry.com/api/v1/resolve?ref=jabrena/plinth/142-java-functional-programming
GET https://markdownregistry.com/api/v1/blob/8c0eada2d90c63cfca17e8770c5d6fed9f98911d8d3302f9289368795d4b2d18

Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.

Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.

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