Customer.statement():
public String statement() {
double totalAmount = 0;
int frequentRenterPoints = 0;
Enumeration rentals = _rentals.elements();
String result = "Rental Record for * " + getName() + "\n";
while(rentals.hasMoreElements()) {
double thisAmount = 0;
Rental each = (Rental)rentals.nextElement(); //取得一筆租借記錄
thisAmount = each.getCharge();
// add frequent renter points(累加常客積點(diǎn))
frequentRenterPoints ++;
if((each.getMovie().getPriceCode() == Movie.NEW_RELEASE) &&
each.getDaysRented() > 1)
frequentRenterPoints ++;
result += "\t" + each.getMovie().getTitle() + "\t" +
String.valueOf(thisAmount) + "\n";
totalAmount += thisAmount;
}
// add footer lines(結(jié)尾打印)
result += "Amount owed is " + String.valueOf(totalAmount) + " \n";
result += "You earned " + String.valueOf(frequentRenterPoints) +
"frequent renter points";
return result;
}
下一件引我注意的事時(shí):thisAmount如今變成多余了.它接受each.getCharge()的執(zhí)行結(jié)果,然后就不再有任何改變.所以我可以運(yùn)用Replace Temp with Query(120)把thisAmount除去:
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(diǎn))
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(jié)尾打印)
result += "Amount owed is " + String.valueOf(totalAmount) + " \n";
result += "You earned " + String.valueOf(frequentRenterPoints) +
"frequent renter points";
return result;
}
我喜歡盡量除去這一類(lèi)臨時(shí)變量.臨時(shí)變量往往形成問(wèn)題.它們會(huì)導(dǎo)致大量參數(shù)被傳來(lái)傳
去,而其實(shí)完全沒(méi)有這種必要.你很容易失去它們的蹤跡,尤其在長(zhǎng)長(zhǎng)的函數(shù)之中更是如此.當(dāng)然我這么做也需付出性能上的代價(jià),例如本例的費(fèi)用就被計(jì)算了兩
次.但是這很容易在Rental class中被優(yōu)化.而且如果代碼有合理的組織和管理,優(yōu)化會(huì)有很好的效果.