144-java-data-oriented-programming

A guide to data-oriented programming in Java, an approach that keeps data structures separate from the code that operates on them. It covers records, immutable data, pure transformations, flat data, validation, and generic data access.

In plain words
What is it for?
Use it when designing Java records and data models, writing side-effect-free transformations and validation, or building reusable data-access code.
Why use it?
It provides consistent ways to make Java data easier to reason about, validate, transform, and change safely.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/jabrena/cursor-rules-examples/144-java-data-oriented-programming
Any agent
npx skills add jabrena/cursor-rules-examples --skill 144-java-data-oriented-programming
Clone the repo
git clone --depth 1 https://github.com/jabrena/cursor-rules-examples

Made for: Claude Code, Codex.

Per session 88 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 548 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00088 $0.00548
Opus 5 $0.00044 $0.00274
Sonnet 5 $0.00018 $0.00110
Haiku 4.5 $0.00009 $0.00055

Measured yesterday against content hash e3308743f1ab, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

144-java-data-oriented-programming scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.agents/skills/144-java-data-oriented-programming/SKILL.md · 42 lines

How it starts

The opening of the file, as written. The whole thing — 42 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Java Data-Oriented Programming Best Practices

Apply data-oriented programming in Java: separate data from behavior with records, use immutable data structures, pure functions for transformations, flat denormalized structures with ID references, generic-to-specific type conversion when needed, pure validation functions, and flexible generic data access layers. All transformations should be explicit, traceable, and composed of clear pure functional steps.

What is covered in this Skill?

  • Separation of concerns: data structures (records, POJOs) vs behavior (utility classes, services)
  • Immutability: records, final fields, transformations produce new instances
  • Pure data transformations: functions depending only on inputs, no side effects
  • Flat and denormalized data: ID references instead of deep nesting
  • Generic until specific: Map<String,Object> for dynamic data, convert to records when processing
  • Data integrity: pure validation functions returning validation results
  • Flexible generic data access: generic CRUD interfaces, interchangeable implementations

Scope: The reference is organized by examples (good/bad code patterns) for each core area. Apply recommendations based on applicable examples.

Constraints

Before applying any data-oriented programming recommendations, ensure the project compiles. Compilation failure is a blocking condition. After applying improvements, run full verification.

  • MANDATORY: Run ./mvnw compile or mvn compile before applying any change
  • SAFETY: If compilation fails, stop immediately — do not proceed until resolved
  • VERIFY: Run ./mvnw clean verify or mvn clean verify after applying improvements
  • BEFORE APPLYING: Read the reference for detailed good/bad examples, constraints, and safeguards for each data-oriented programming pattern

When to use this skill

  • Review Java code for data-oriented programming
  • Apply best practices for data-oriented programming in Java code

Reference

Read the full file on GitHub · 42 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 42 lines · 88 tokens per session scan A e3308743f1ab

Subscribe to this mod's changes

144-java-data-oriented-programming is a skill published in the GitHub repository jabrena/cursor-rules-examples (2 stars, last pushed 5d ago), licensed Apache-2.0. It adds 88 tokens to every session and 548 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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