java-best-practices

Included with Lifetime

$97 forever

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.

Design

What this skill does

# 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](references/example.md)

Files: 3

Size: 7.0 KB

Complexity: 26/100

Category: Design

Source: https://github.com/hoangnguyen0403/agent-skills-standard/tree/main/skills/java/java-best-practices

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