java-fundamentals skill

---
name: java-fundamentals
description: Master core Java programming - syntax, OOP, collections, streams, and exception handling
sasmp_version: "1.3.0"
version: "3.0.0"
bonded_agent: 01-java-fundamentals
bond_type: PRIMARY_BOND
allowed-tools: Read, Write, Bash, Glob, Grep

# Parameter Validation
parameters:
  java_version:
    type: string
    default: "21"
    enum: ["8", "11", "17", "21"]
  topic:
    type: string
    enum: [syntax, oop, collections, streams, exceptions, generics]
---

# 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

```java
// 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

| Need | Use | Reason |
|------|-----|--------|
| Indexed access | ArrayList | O(1) random access |
| Unique elements | HashSet | O(1) contains |
| Sorted unique | TreeSet | O(log n) sorted |
| Key-value pairs | HashMap | O(1) get/put |

## Troubleshooting

| Problem | Cause | Solution |
|---------|-------|----------|
| NullPointerException | Null reference | Use Optional |
| ConcurrentModificationException | Modify during iteration | Iterator.remove() |
| ClassCastException | Wrong type | Use generics |

## Usage

```
Skill("java-fundamentals")
```