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Java Fundamentals

  • 569 installs
  • 40 repo stars
  • Updated January 5, 2026
  • pluginagentmarketplace/custom-plugin-java

java-fundamentals is a Claude Code skill that generates clean, idiomatic Java code for backend services, APIs, and agent components using modern Java 8–21 patterns for developers who need production-quality core language

About

java-fundamentals is a Java & JVM skill at version 3.0.0 that teaches agents to write production-quality core Java for backend services, APIs, and agent components. It parameterizes java_version across 8, 11, 17, and 21 and topic across six areas: syntax, OOP, collections, streams, exceptions, and generics. Allowed tools include Read, Write, Bash, Glob, and Grep so agents can scaffold and edit real project files. Developers reach for java-fundamentals when bootstrapping Spring-style services, CLI utilities, or JVM agent modules and want idiomatic patterns instead of outdated Java 7-era snippets. The skill bonds to agent 01-java-fundamentals under SASMP 1.3.0 for marketplace plugin workflows.

  • Covers syntax, OOP, collections, streams, and exception handling for Java 8–21
  • Enforces SOLID principles and production-quality patterns
  • Supports Records, sealed classes, pattern matching and functional streams
  • Includes 6 focused learning and generation topics: syntax, oop, collections, streams, exceptions, generics
  • Bonded agent with Read, Write, Bash, Glob, Grep tools for direct codebase work

Java Fundamentals by the numbers

  • 569 all-time installs (skills.sh)
  • +8 installs in the week ending Aug 4, 2026 (Skillselion tracking)
  • Ranked #715 of 4,347 Backend & APIs skills by installs in the Skillselion catalog
  • Data as of Aug 4, 2026 (Skillselion catalog sync)
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Listed on Skillselion
Installs569
repo stars40
Last updatedJanuary 5, 2026
Repositorypluginagentmarketplace/custom-plugin-java

How do you write idiomatic modern Java backend code?

Generate clean, idiomatic Java code for backend services, APIs, and agent components using modern Java 8–21 patterns.

Who is it for?

Developers scaffolding JVM backend services or agent components who need version-aware Java 8 through 21 fundamentals in agent-assisted coding.

Skip if: Teams seeking Spring Boot-specific wiring, Android UI patterns, or advanced concurrency frameworks beyond core language fundamentals.

When should I use this skill?

A user asks for Java syntax, OOP, collections, streams, generics, or exception handling in a backend or API module.

What you get

Production-ready Java source files with typed collections, streams, generics, and exception handling

  • Java source files
  • Backend service scaffolds
  • Idiomatic API handler examples

By the numbers

  • Covers 6 topic areas: syntax, OOP, collections, streams, exceptions, and generics
  • Supports 4 Java versions: 8, 11, 17, and 21
  • Skill version 3.0.0 with SASMP 1.3.0 bonding

Files

SKILL.mdMarkdownGitHub ↗

Java Fundamentals Skill

Master core Java programming with production-quality patterns.

Overview

This skill covers Java fundamentals including syntax, OOP, collections, streams API, and exception handling for Java 8-21.

When to Use This Skill

Use when you need to:

  • Write clean, idiomatic Java code
  • Design classes following OOP principles
  • Choose appropriate collection types
  • Implement functional programming patterns
  • Handle exceptions properly

Topics Covered

Core Syntax (Java 8-21)

  • Variables, data types, operators
  • Control flow, methods, classes
  • Records (Java 16+), sealed classes (Java 17+)
  • Pattern matching (Java 21)

Object-Oriented Programming

  • Classes, inheritance, polymorphism
  • Interfaces and abstract classes
  • SOLID principles

Collections Framework

  • List: ArrayList, LinkedList
  • Set: HashSet, TreeSet
  • Map: HashMap, ConcurrentHashMap
  • Queue: ArrayDeque, PriorityQueue

Streams API

  • filter, map, flatMap, reduce, collect
  • Optional handling
  • Parallel streams

Exception Handling

  • Checked vs unchecked exceptions
  • Try-with-resources
  • Custom exceptions

Quick Reference

// Record (Java 16+)
public record User(String name, String email) {}

// Pattern matching (Java 21)
String format(Object obj) {
    return switch (obj) {
        case Integer i -> "Int: %d".formatted(i);
        case String s -> "String: %s".formatted(s);
        default -> obj.toString();
    };
}

// Stream operations
List<String> names = users.stream()
    .filter(User::isActive)
    .map(User::getName)
    .sorted()
    .toList();

// Optional handling
String name = Optional.ofNullable(user)
    .map(User::getName)
    .orElse("Unknown");

Collection Selection

NeedUseReason
Indexed accessArrayListO(1) random access
Unique elementsHashSetO(1) contains
Sorted uniqueTreeSetO(log n) sorted
Key-value pairsHashMapO(1) get/put

Troubleshooting

ProblemCauseSolution
NullPointerExceptionNull referenceUse Optional
ConcurrentModificationExceptionModify during iterationIterator.remove()
ClassCastExceptionWrong typeUse generics

Usage

Skill("java-fundamentals")

Related skills

FAQ

Which Java versions does java-fundamentals support?

java-fundamentals accepts java_version values 8, 11, 17, and 21 through its parameter enum. Agents generate idiomatic code aligned with the selected release rather than mixing deprecated APIs.

What topics does java-fundamentals cover?

java-fundamentals spans six topics: syntax, OOP, collections, streams, exceptions, and generics. The skill focuses on core language patterns for backend services, APIs, and agent components.

Backend & APIsbackendintegrations

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