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java-fundamentals — Claude Code skill: what it does, how to install

Guides coding assistants through modern Java development from version 8 to 21, including Streams, collections, records, and OOP patterns.

Install into Claude Code · Skills CLI (Vercel) All methods and platforms ↓ 
npx skills add pluginagentmarketplace/custom-plugin-java --skill java-fundamentals -a claude-code
Open on GitHub

What java-fundamentals does

This skill equips your coding agent with conventions across Java versions 8, 11, 17, and 21. It covers object-oriented design, collections, stream transformations, generics, and exception handling. Version 21 is the default.

The skill defines data structure choices based on complexity, favoring HashSet for O(1) membership lookups and TreeSet for O(log n) ordered data. Your agent receives access to Read, Write, Bash, Glob, and Grep to inspect and modify project files.

Because the skill defaults to Java 21, projects on legacy versions like Java 8 require specifying the java_version parameter to avoid unsupported switch syntax or records.

What it helps with

  • refactor nested loops into functional Stream pipelines
  • select appropriate collection types based on algorithmic complexity
  • convert verbose POJOs into compact Java records
  • replace risky null dereferences with safe Optional patterns

Example prompts for the agent

  • Refactor this data processing loop into a Java 21 stream pipeline with toList().
  • Convert this mutable DTO class into a record.
  • Pick the right collection for fast lookups by key and explain the choice.

How to install java-fundamentals

1Skills CLI (Vercel)

npx skills add pluginagentmarketplace/custom-plugin-java --skill java-fundamentals -a claude-code

2Manually: put the files in place

~/.claude/skills/java-fundamentals/SKILL.md

Copy the whole skill folder; for one project use .claude/skills/java-fundamentals/

Step by step, with commands for each platform: How to install skills in Claude Code: five ways

Questions about java-fundamentals

How to install java-fundamentals in Claude Code?

Run npx skills add pluginagentmarketplace/custom-plugin-java --skill java-fundamentals -a claude-code in your terminal.

What Java versions does java-fundamentals cover?

It supports Java 8, 11, 17, and 21, defaulting to version 21. You can pass a specific version parameter when targeting older runtimes.

Which environment tools does this skill invoke?

The skill configures permissions for Read, Write, Bash, Glob, and Grep to search and modify repository files.

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