java-refactoring-extract-method
Refactoring using Extract Methods in Java Language
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/github/awesome-copilot --skill java-refactoring-extract-method- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads java-refactoring-extract-method automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
Security audits
Independent scans of the skill's instructions and bundled files.
SKILL.md
The instructions your agent reads when the skill is triggered.
Refactoring Java Methods with Extract Method
Role
You are an expert in refactoring Java methods.
Below are 2 examples (with titles code before and code after refactoring) that represents Extract Method.
Code Before Refactoring 1:
public FactLineBuilder setC_BPartner_ID_IfValid(final int bpartnerId) {
assertNotBuild();
if (bpartnerId > 0) {
setC_BPartner_ID(bpartnerId);
}
return this;
}
Code After Refactoring 1:
public FactLineBuilder bpartnerIdIfNotNull(final BPartnerId bpartnerId) {
if (bpartnerId != null) {
return bpartnerId(bpartnerId);
} else {
return this;
}
}
public FactLineBuilder setC_BPartner_ID_IfValid(final int bpartnerRepoId) {
return bpartnerIdIfNotNull(BPartnerId.ofRepoIdOrNull(bpartnerRepoId));
}
Code Before Refactoring 2:
public DefaultExpander add(RelationshipType type, Direction direction) {
Direction existingDirection = directions.get(type.name());
final RelationshipType[] newTypes;
if (existingDirection != null) {
if (existingDirection == direction) {
return this;
}
newTypes = types;
} else {
newTypes = new RelationshipType[types.length + 1];
System.arraycopy(types, 0, newTypes, 0, types.length);
newTypes[types.length] = type;
}
Map<String, Direction> newDirections = new HashMap<String, Direction>(directions);
newDirections.put(type.name(), direction);
return new DefaultExpander(newTypes, newDirections);
}
Code After Refactoring 2:
public DefaultExpander add(RelationshipType type, Direction direction) {
Direction existingDirection = directions.get(type.name());
final RelationshipType[] newTypes;
if (existingDirection != null) {
if (existingDirection == direction) {
return this;
}
newTypes = types;
} else {
newTypes = new RelationshipType[types.length + 1];
System.arraycopy(types, 0, newTypes, 0, types.length);
newTypes[types.length] = type;
}
Map<String, Direction> newDirections = new HashMap<String, Direction>(directions);
newDirections.put(type.name(), direction);
return (DefaultExpander) newExpander(newTypes, newDirections);
}
protected RelationshipExpander newExpander(RelationshipType[] types,
Map<String, Direction> directions) {
return new DefaultExpander(types, directions);
}
Safety Rules
- Behaviour-preserving only: no functional change, no removed logic, no changed exceptions, side-effect order or visibility of the original method.
- Baseline first: run the narrowest green test command for the code (
./mvnw -q -Dtest=MyTest test,./gradlew test --tests MyTest) or./mvnw verify/./gradlew build. Re-run it after every extraction. If the baseline is red, stop and report. - If the code has no tests, stop and report; propose characterization tests first. Never delete or weaken tests.
- One extraction per step (one commit each when the user asks for commits) so each is reviewable and revertible.
- Prefer the IDE refactoring: use an available IDE tool that exposes Extract Method (it handles parameters and return values safely). The Copilot CLI
lsptool offers navigation and rename but no code actions, so configuring jdtls throughlsp-setupdoes not provide it; otherwise extract by hand and validate with the compiler and tests. - Extracted methods are
privateby default. Do not add public/protected methods, change the existing signature, or touch generated code (target/,build/generated,@Generated) without asking the user. - Watch for: local variables modified in the block (return a value or introduce a small result type), multiple results, checked exceptions,
return/break/continueinside the block, andsynchronized/transaction-annotated methods (extractedprivatemethods called onthisbypass Spring proxies and AOP).
Task
Apply Extract Method to improve readability, testability, cohesion and consistency.
- Identify candidate methods (rough guide: > 15 lines, > 10 statements or cyclomatic complexity > 10) and cohesive blocks inside them.
- Extract each block into a descriptively named method, following the existing code style and the project's Java level (check
maven.compiler.release/ toolchain; do not use newer syntax). - Add a one-line comment above each new method only if its name does not already convey its purpose.
- Compile and run the tests; report the methods changed, the commands run and their results.
Output complete, compilable code for each changed method.
Code to be Refactored:
Now, assess all methods with high complexity and refactor them using Extract Method
FAQ
What does the java-refactoring-extract-method skill do?
Refactoring using Extract Methods in Java Language
How do I install java-refactoring-extract-method?
Run npx skills add https://github.com/github/awesome-copilot --skill java-refactoring-extract-method in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/java-refactoring-extract-method/ (personal) or .claude/skills/java-refactoring-extract-method/ (project).
Which AI agents can use java-refactoring-extract-method?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is java-refactoring-extract-method safe to install?
Security partners have reviewed it: Gen Agent Trust Hub passed; Socket passed; Snyk passed; Runlayer flagged items to review; ZeroLeaks passed. As with any skill, read the SKILL.md and bundled scripts before installing.
Who maintains java-refactoring-extract-method?
It is published by github in github/awesome-copilot, and it is an official skill from the maker of the technology it covers. It has 9,297 recorded installs.
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