提取[常客積點計算]代碼
首先我們需要針對[常客積點計算]這部分代碼（以下粗體部分）運用Extract Method(110)重構準則:
public String statement() {
double totalAmount = 0;
int frequentRenterPoints = 0;
Enumeration rentals = _rentals.elements();
String result = "Rental Record for * " + getName() + "\n";
while(rentals.hasMoreElements()) {
Rental each = (Rental)rentals.nextElement(); //取得一筆租借記錄
// add frequent renter points(累加常客積點)
frequentRenterPoints ++;
if((each.getMovie().getPriceCode() == Movie.NEW_RELEASE) &&
each.getDaysRented() > 1)
frequentRenterPoints ++;
result += "\t" + each.getMovie().getTitle() + "\t" +
String.valueOf(each.getCharge()) + "\n";
totalAmount += each.getCharge();
}
// add footer lines(結尾打印)
result += "Amount owed is " + String.valueOf(totalAmount) + " \n";
result += "You earned " + String.valueOf(frequentRenterPoints) +
"frequent renter points";
return result;
}
再一次我又要尋找局部變量。這里再一次用到了each,而它可以被當作參數傳入新函數中。另一個臨時變量是frequentRenterPoints。本
例中的它在被使用之前已經先有初值，但提煉出來的函數并沒有讀取改值，所以我們不需要將它當作參數傳進去，只需對它執行[付添賦值操作](appending assignment,operator+=)就行了。
public String statement() {
double totalAmount = 0;
int frequentRenterPoints = 0;
Enumeration rentals = _rentals.elements();
String result = "Rental Record for * " + getName() + "\n";
while(rentals.hasMoreElements()) {
Rental each = (Rental)rentals.nextElement(); //取得一筆租借記錄
frequentRenterPointers += each.getFrequentRenterPoints();
result += "\t" + each.getMovie().getTitle() + "\t" +
String.valueOf(each.getCharge()) + "\n";
totalAmount += each.getCharge();
}
// add footer lines(結尾打印)
result += "Amount owed is " + String.valueOf(totalAmount) + " \n";
result += "You earned " + String.valueOf(frequentRenterPoints) +
"frequent renter points";
return result;
}
class Rental...
int getFrequentRenterPoints() {
if((getMovie().getPriceCode() == Movie.NEW_RELEASE)
&& getDaysRented() > 1)
return 2;
else
return 1;
}