java-refactoring-extract-method

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Refactoring using Extract Methods in Java Language

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🧩 One of 7 skills in the github/awesome-copilot package — works on its own, and pairs well with its siblings.

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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);
}

Task

Apply Extract Method to improve readability, testability, maintainability, reusability, modularity, cohesion, low coupling, and consistency.

Always return a complete and compilable method (Java 17).

Perform intermediate steps internally:

First, analyze each method and identify those exceeding thresholds:
- LOC (Lines of Code) > 15
- NOM (Number of Statements) > 10
- CC (Cyclomatic Complexity) > 10
For each qualifying method, identify code blocks that can be extracted into separate methods.
Extract at least one new method with a descriptive name.
Output only the refactored code inside a single java block.
Do not remove any functionality from the original method.
Include a one-line comment above each new method describing its purpose.

Code to be Refactored:

Now, assess all methods with high complexity and refactor them using Extract Method