Java Core Skill

REFERENCE MODE: This skill provides reference material. Load specific standards on-demand based on current task.

Core Java development standards for general Java projects. This skill covers fundamental patterns, modern Java features, performance optimization, and implementation verification.

Prerequisites

This skill applies to Java 17+ projects with no CUI-specific dependencies.

Workflow

Step 1: Load Core Patterns

CRITICAL: Load this standard for any Java implementation work.

Read: standards/java-core-patterns.md

This provides foundational rules for:

• Package and class structure
• Method design and command-query separation
• Parameter objects and method complexity
• Code organization principles

Step 2: Load Additional Standards (As Needed)

Modern Java Features (load for new code):

Read: standards/java-modern-features.md

Use when: Writing new code or modernizing existing code. Covers records, pattern matching, sealed classes, and text blocks.

Performance Patterns (load for optimization work):

Read: standards/java-performance-patterns.md

Use when: Optimizing code or designing high-performance components.

Build Precondition Pattern (load for validation logic):

Read: standards/build-precondition-pattern.md

Use when: Implementing validation logic or precondition checking.

Implementation Verification (load for code review):

Read: standards/implementation-verification.md

Use when: Reviewing implementations or verifying code quality.

Key Rules Summary

Package Structure

// CORRECT - Feature-based organization
de.example.portal.authentication     // Authentication feature
de.example.portal.configuration      // Configuration feature
de.example.portal.user.management    // User management feature

Command-Query Separation

// Query - returns value, no side effects
public boolean isValid() {
    return status == Status.VALID;
}

// Command - modifies state, returns void
public void markAsInvalid() {
    this.status = Status.INVALID;
}

Parameter Objects (3+ parameters)

// CORRECT - Multiple related parameters grouped
public record ValidationRequest(
    String tokenId,
    Set<String> expectedScopes,
    Duration maxAge,
    String issuer
) {}

public boolean validate(ValidationRequest request) {
    // Clear, organized parameters
}

Related Skills

• pm-dev-java:java-null-safety

  - JSpecify null annotations

• pm-dev-java:java-lombok

  - Lombok patterns

• pm-dev-java:junit-core

  - JUnit 5 testing patterns

• pm-dev-java:javadoc

  - JavaDoc documentation standards

Standards Reference

Standard	Purpose
java-core-patterns.md	Code organization and design principles
java-modern-features.md	Records, pattern matching, sealed classes
java-performance-patterns.md	Performance optimization patterns
build-precondition-pattern.md	Validation logic patterns
implementation-verification.md	Code review and verification