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Modern Java Development Guidelines (Java 8+) · jabrena | DecimalAI

codingby jabrena

Modern Java Development Guidelines (Java 8+)

jabrena/141-java-refactoring-with-modern-features

Source jabrena/plinth ↗License Apache-2.0

Use when you need to refactor Java code to adopt modern Java features (Java 8+) — including migrating anonymous classes to lambdas, replacing Iterator loops with Stream API, adopting Optional for null safety, switching from legacy Date/Calendar to java.time, using collection factory methods, applying text blocks, var inference, or leveraging Java 25 features like flexible constructor bodies and module import declarations. This should trigger for requests such as Review Java code for modern Java

NewMaintained

Automatic

Coding pack

Last verified 8/20/2026

What it changes

Passed 9 of 16 test cases with the skill, and 10 of 16 without it.

Without skill64%

With skill59%

Checks it passed that the model alone missed

Executes Maven compile before applying refactorings
Refers to the modern Java reference documentation in references/141-java-refactoring-with-modern-features.md

2 fixed11 passed either way6 still failing3 broke

Pass-rate lift: -5 pp
Tokens: +11%
Agent turns: 0%
Response time: -32%

Model gemini-3.6-flashMeasured 8/20/2026v113 of 22 cases passed with skill · 16 comparable

Tokens, turns and time describe resource use, not a dollar price.

Use this skill

Save it into your project's skills folder. Claude Code picks it up in its next session.

curl -fsSL --create-dirs -o .claude/skills/jabrena-141-java-refactoring-with-modern-features/SKILL.md https://app.decimal.ai/s/jabrena-141-java-refactoring-with-modern-features/SKILL.md

Want it pinned and updatable? pip install "decimalai>=0.15", then decimalai skills add jabrena-141-java-refactoring-with-modern-features, and start Claude Code with claude --plugin-dir "$(git rev-parse --show-toplevel)/.agents"

1 · One-time — install the CLI (docs ↗)

pip install "decimalai>=0.15"

2 · Get the skill — writes .agents/skills/jabrena-141-java-refactoring-with-modern-features/ and pins it in .decimal/skills.lock

decimalai skills add jabrena-141-java-refactoring-with-modern-features

No CLI? Get the same file — curl · raw file

curl -fsSL --create-dirs -o .claude/skills/jabrena-141-java-refactoring-with-modern-features/SKILL.md https://app.decimal.ai/s/jabrena-141-java-refactoring-with-modern-features/SKILL.md

Raw file: /s/jabrena-141-java-refactoring-with-modern-features/SKILL.md ↗ · machine-readable summary at /s/jabrena-141-java-refactoring-with-modern-features.json ↗

Safety checks: 3 of 3 passed

Code scan CleanIntent PassedContent Clean

See it in action

One of 2 test cases the skill fixed. Same model, same prompt, with and without the skill.

1 of 2

Prompt

Before applying modern Java refactoring to `AccountService.java`, what specific Maven command must be executed first?

What was checked, without and with the skill
Checked	Without skill	With skill
Executes Maven compile before applying refactorings	Missed	Passed

case-18 · gemini-3.6-flash · 8/20/2026 · answers are capped and redacted

What's inside

The instructions your model reads when the skill loads.

SKILL.md58 lines2 files

Modern Java Development Guidelines (Java 8+)

Identify and apply modern Java (Java 8+) refactoring opportunities to improve readability, maintainability, and performance.

What is covered in this Skill?

Lambda expressions and method references (over anonymous classes)
Stream API for declarative collection processing
Optional for null-safe APIs
java.time API (replacing Date/Calendar)
Default interface methods, var type inference
Unmodifiable collection factory methods (List.of(), Set.of(), Map.of())
Text blocks for multi-line strings
Java 25 Flexible Constructor Bodies (JEP 513)
Java 25 Module Import Declarations (JEP 511)

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 modern Java refactoring, ensure the project compiles. If compilation fails, stop immediately — do not proceed until the project compiles successfully. After applying improvements, run full verification.

MANDATORY: Run ./mvnw compile or mvn compile before applying any changes
SAFETY: If compilation fails, stop immediately — do not proceed until the project compiles successfully
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 modern Java feature
EDGE CASE: If request scope is ambiguous, stop and ask a clarifying question before applying changes
EDGE CASE: If required inputs, files, or tooling are missing, report what is missing and ask whether to proceed with setup guidance

When to use this skill

Review Java code for modern Java development
Apply best practices for modern Java development in Java code
Modernize Java code with records pattern matching or switch expressions
Replace legacy idioms with modern Java features
Adopt Java 8+ language features safely

Workflow

Compile project before modernization

Track record

Benchmark

9 / 16

test cases passed, vs 10 / 16 without

Adoption

Users: 0
Times used: 0

Safety and source details

SkillSafety

✓ 3 of 3 passed

Code scan15 of 15 checks clean

0 critical · 0 warning · 0 info — scanner v4 — 8/3/2026

View 15 scanner checks

live_secretremote_code_executionreverse_shelldata_exfiltrationssrf_metadataagent_snoopinganti_refusaldestructive_commandsobfuscated_unicodeunicode_homoglyphopaque_blobsuspicious_urltool_overreachtrigger_abuseprompt_injection_phrasing

IntentSafe

LLM judge · does the skill do what it claims

ContentClean

LLM judge · policy & harmful-content review

Source

Imported

jabrena / plinth

skills/141-java-refactoring-with-modern-features/SKILL.md

View on GitHub ↗

License Apache-2.0Imported 10/2/2026Version v1Bundled 1 file

Other skills for the same job

Published skills whose descriptions closely match this one, with their headline benchmark lift.

jabrena/142-java-functional-programmingUse when you need to apply functional programming principles in Java — including writing immutable objects and Records, pure functions, functional interfaces, lambda expressions, Stream API pipelines, Optional for null safety, function composition, higher-order functions, pattern matching for instanceof and switch, sealed classes/interfaces for controlled hierarchies, Stream Gatherers for custom operations, currying/partial application, effect boundary separation, and concurrent-safe functional Close match-9 pp pass-rate lift

More skills from the same source and nearby in the registry, with their headline benchmark lift.

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See it in action

What's inside

Modern Java Development Guidelines (Java 8+)

Constraints

When to use this skill

Workflow

Track record

Benchmark

Adoption

SkillSafety

Source

Other skills for the same job

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