cuioss/java-core

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, and performance optimization.

Prerequisites

This skill applies to Java 21+ projects. For projects using CuiLogger, LogRecord, or other libraries from the pm-dev-java-cui bundle, load that bundle's skills additionally.

Workflow

Step 1: Load Core Patterns

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)

Java 17 Features (load for new code):

Read: standards/java-17-features.md

Use when: Writing new code or modernizing existing code. Covers records, switch expressions, pattern matching for instanceof, sealed classes, text blocks, streams, and Optional usage.

Java 21 Features (load for Java 21+ code):

Read: standards/java-21-features.md

Use when: Using Java 21 features — pattern matching in switch, record patterns, sequenced collections, and virtual threads.

Java 25 Features (load for Java 25+ code):

Read: standards/java-25-features.md

Use when: Using Java 25 features — scoped values, flexible constructor bodies, module imports, compact source files, KDF API, and JVM performance flags (AOT cache, compact headers).

Concurrency Patterns (load for multi-threaded code):

Read: standards/java-concurrency.md

Use when: Writing concurrent or multi-threaded code. Covers why to avoid volatile/double-checked locking, lock selection (ReentrantLock, StampedLock, atomics), virtual thread rules, ScopedValue vs ThreadLocal, concurrent collections, and common pitfalls.

Performance Patterns (load for optimization work):

Read: standards/java-performance-patterns.md

Use when: Optimizing code or designing high-performance components. Covers string handling, autoboxing, collection sizing, thread safety, exception handling, and logging performance.

DSL-Style Nested Constants (load for constant organization):

Read: standards/dsl-constants.md

Use when: Organizing related constants hierarchically using nested static classes with @UtilityClass. Covers configuration keys, error codes, resource bundles, logging messages, and best practices.

Security (input validation, secure logging, secrets, startup validation):

The Java security surface — inbound input validation (java-input-validation.md) and outbound security patterns (java-security-patterns.md) — is owned by Skill: pm-dev-java:java-security, and both standards files now live under THAT skill's standards/ directory (not this one). Load pm-dev-java:java-security for any security-sensitive review or hardening task; it resolves through the security profile. The cross-cutting OWASP/STRIDE/secrets/secure-logging/trust-boundary foundations live in Skill: plan-marshall:persona-security-expert.

Related Skills

• plan-marshall:ref-code-quality - Language-agnostic code quality principles
• 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