Java Fundamentals
This is your baseline Java reference for everything from classic OOP patterns to modern Java 21 features like pattern matching and records. It covers the core language mechanics you'll use daily: collections selection (with an actual decision table for ArrayList vs HashSet vs TreeSet), streams operations, exception handling, and SOLID principles. The quick reference examples are genuinely helpful, showing real patterns like Optional chaining and switch expressions. It spans Java 8 through 21, so you can write code that works across different runtime versions. Think of it as the skill you invoke when you need clean, idiomatic Java without reaching for Stack Overflow every time you forget whether to use flatMap or just map.
- skills.sh installs
- 624
- GitHub stars
- 42
- last updated
- Aug 21, 2026
Install
$ npx -y skills add pluginagentmarketplace/custom-plugin-java --skill java-fundamentals --agent claude-codeInstalls into .claude/skills of the current project.
Files
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
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- Repository
- github.com/pluginagentmarketplace/custom-plugin-java
- Categories
- Debugging, Java & JVM
- First seen
- Jun 3, 2026
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