1. Refactorings
Luke Marsh

2. Three Refactorings Replace Parameter With Method
Simplifying method calls
Remove Assignment to Parameters
Clarifying which objects are modified
Hide Method
Making methods private

3. Replace Parameters with Method
public double getPrice() { int basePrice = _quantity * _itemPrice; int discountLevel; if (_quantity > 100) discountLevel = 2; else discountLevel = 1; double finalPrice = discountedPrice (basePrice, discountLevel); return finalPrice; }
private double discountedPrice (int basePrice, int discountLevel) { if (discountLevel == 2) return basePrice * 0.1; else return basePrice * 0.05; }
Motivation: If it’s possible for the method to get a parameter by other means, it should do so. Long parameter lists should be simplified when possible.

4. Replace Parameters with Method
First Replacement:
public double getPrice() { int basePrice = _quantity * _itemPrice; double finalPrice = discountedPrice (basePrice); return finalPrice; }
private double discountedPrice (int basePrice) { if (getDiscountLevel() == 2) return basePrice * 0.1; else return basePrice * 0.05; }
private int getDiscountLevel() { if (_quantity > 100) return 2; else return 1; }

5. Replace Parameters with Method
First Replacement:
public double getPrice() { int basePrice = _quantity * _itemPrice; double finalPrice = discountedPrice (basePrice); return finalPrice; }
private double discountedPrice (int basePrice) { if (getDiscountLevel() == 2) return basePrice * 0.1; else return basePrice * 0.05; }
private int getDiscountLevel() { if (_quantity > 100) return 2; else return 1; }
Second Replacement:
public double getPrice() { return discountedPrice (); }
private double discountedPrice () { if (getDiscountLevel() == 2) return getBasePrice() * 0.1; else return getBasePrice() * 0.05; }
private double getBasePrice() { return _quantity * _itemPrice; }

6. Replace Parameters with Method
Benefit: Long parameters can cause confusion. The more parameters for a method, the more information the user needs to keep track of when calling the method.

7. Remove Assignments to Parameters
Example:
int discount (int inputVal, int quantity, int yearToDate) { if (inputVal > 50) inputVal -= 2; if (quantity > 100) inputVal -= 1; if (yearToDate > 10000) inputVal -= 4; return inputVal; }
Motivation: Changes to a parameter object, in a pass by value scenario, are not reflected in the calling routine. Furthermore, it leads to confusion in what object is being modified.

8. Remove Assignments to Parameters
Easy Solution:
int discount (int inputVal, int quantity, int yearToDate) { int result = inputVal; if (inputVal > 50) result -= 2; if (quantity > 100) result -= 1; if (yearToDate > 10000) result -= 4; return result; }
Benefit: No confusion as to which object is being modified, also makes this method function correctly in pass by value scenarios.

9. Hide Method
Example:
public int getMiles(){ public void setMiles (int x) { return miles; } miles = x;
Motivation: Not all methods need to be visible, such as setter and getter methods.
Solution: Set the method from public to private.
Benefit: As your class grows, some methods don’t need to be accessed publicly, more specifically if it isn’t called by any other classes.

10. Any Questions?