Agent-skills-standard java-best-practices

Apply core Effective Java patterns for robust, maintainable code. Use when applying SOLID principles, choosing between inheritance and composition, refactoring Java code smells, or reviewing class design. (triggers: **/*.java, refactor, SOLID, builder, factory, composition, immutable, Optional, checked exception, clean code)

install

source · Clone the upstream repo

git clone https://github.com/HoangNguyen0403/agent-skills-standard

Claude Code · Install into ~/.claude/skills/

T=$(mktemp -d) && git clone --depth=1 https://github.com/HoangNguyen0403/agent-skills-standard "$T" && mkdir -p ~/.claude/skills && cp -r "$T/skills/java/java-best-practices" ~/.claude/skills/hoangnguyen0403-agent-skills-standard-java-best-practices && rm -rf "$T"

manifest: skills/java/java-best-practices/SKILL.md

source content

Java Best Practices

Priority: P1 (HIGH)

Implementation Guidelines

Immutability: Prefer immutable objects (
```
final
```
fields, unmodifiable collections).
Access Modifiers: Minimize visibility. Default to package-private (no modifier). Use
```
private
```
for all fields. Only
```
public
```
for API contracts.
Composition > Inheritance: Favor
```
Has-A
```
over
```
Is-A
```
. Avoid deep hierarchies.
Constructors: Use Static Factory Methods (
```
User.of()
```
) over complex constructors.
Builder Pattern: Use for objects with 4+ parameters.
Exceptions: Recoverable → Checked; Programming error → Unchecked.
Fail Fast: Validate parameters (
```
Objects.requireNonNull
```
) at method start.
Interfaces: Code to interfaces (
```
List
```
,
```
Map
```
), not implementations (
```
ArrayList
```
).
Dependency Injection: Inject dependencies via constructor; don't create them internally.
Method References: Use
```
String::toUpperCase
```
over
```
s -> s.toUpperCase()
```
where readable.

Anti-Patterns

No Null Returns: Return Optional<T> or empty collection instead.
No Empty Catch: Log or rethrow; never swallow exceptions silently.
No God Class: Split into focused classes following Single Responsibility Principle.
No Magic Numbers: Extract named constants with clear meaning.
No Mutable Statics: Avoid public static mutable fields (global state).

References

Static Factory & Composition Examples