java-refactoring-extract-method

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 lsp tool offers navigation and rename but no code actions, so configuring jdtls through lsp-setup does not provide it; otherwise extract by hand and validate with the compiler and tests.
• Extracted methods are private by 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/continue inside the block, and synchronized/transaction-annotated methods (extracted private methods called on this bypass Spring proxies and AOP).

Task

Apply Extract Method to improve readability, testability, cohesion and consistency.

1. Identify candidate methods (rough guide: > 15 lines, > 10 statements or cyclomatic complexity > 10) and cohesive blocks inside them.
2. 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).
3. Add a one-line comment above each new method only if its name does not already convey its purpose.
4. 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