学习《重构手册》

void printOwing() {
  printBanner();

// Print details.
  System.out.println("name: " + name);
  System.out.println("amount: " + getOutstanding());
}

void printOwing() {
  printBanner();
  printDetails(getOutstanding());
}

void printDetails(double outstanding) {
  System.out.println("name: " + name);
  System.out.println("amount: " + outstanding);
}

class PizzaDelivery {
  // ...
  int getRating() {
    return moreThanFiveLateDeliveries() ? 2 : 1;
  }
  boolean moreThanFiveLateDeliveries() {
    return numberOfLateDeliveries > 5;
  }
}

class PizzaDelivery {
  // ...
  int getRating() {
    return numberOfLateDeliveries > 5 ? 2 : 1;
  }
}

void renderBanner() {
  if ((platform.toUpperCase().indexOf("MAC") > -1) &&
       (browser.toUpperCase().indexOf("IE") > -1) &&
        wasInitialized() && resize > 0 )
  {
    // do something
  }
}

void renderBanner() {
  final boolean isMacOs = platform.toUpperCase().indexOf("MAC") > -1;
  final boolean isIE = browser.toUpperCase().indexOf("IE") > -1;
  final boolean wasResized = resize > 0;

if (isMacOs && isIE && wasInitialized() && wasResized) {
    // do something
  }
}

boolean hasDiscount(Order order) {
  double basePrice = order.basePrice();
  return basePrice > 1000;
}

boolean hasDiscount(Order order) {
  return order.basePrice() > 1000;
}

double calculateTotal() {
  double basePrice = quantity * itemPrice;
  if (basePrice > 1000) {
    return basePrice * 0.95;
  }
  else {
    return basePrice * 0.98;
  }
}

double calculateTotal() {
  if (basePrice() > 1000) {
    return basePrice() * 0.95;
  }
  else {
    return basePrice() * 0.98;
  }
}
double basePrice() {
  return quantity * itemPrice;
}

double temp = 2 * (height + width);
System.out.println(temp);
temp = height * width;
System.out.println(temp);

final double perimeter = 2 * (height + width);
System.out.println(perimeter);
final double area = height * width;
System.out.println(area);

int discount(int inputVal, int quantity) {
  if (inputVal > 50) {
    inputVal -= 2;
  }
  // ...
}

int discount(int inputVal, int quantity) {
  int result = inputVal;
  if (inputVal > 50) {
    result -= 2;
  }
  // ...
}

class Order {
  // ...
  public double price() {
    double primaryBasePrice;
    double secondaryBasePrice;
    double tertiaryBasePrice;
    // Perform long computation.
  }
}

class Order {
  // ...
  public double price() {
    return new PriceCalculator(this).compute();
  }
}

class PriceCalculator {
  private double primaryBasePrice;
  private double secondaryBasePrice;
  private double tertiaryBasePrice;

public PriceCalculator(Order order) {
    // Copy relevant information from the
    // order object.
  }

public double compute() {
    // Perform long computation.
  }
}

String foundPerson(String[] people){
  for (int i = 0; i < people.length; i++) {
    if (people[i].equals("Don")){
      return "Don";
    }
    if (people[i].equals("John")){
      return "John";
    }
    if (people[i].equals("Kent")){
      return "Kent";
    }
  }
  return "";
}

String foundPerson(String[] people){
  List candidates =
    Arrays.asList(new String[] {"Don", "John", "Kent"});
  for (int i=0; i < people.length; i++) {
    if (candidates.contains(people[i])) {
      return people[i];
    }
  }
  return "";
}

class Report {
  // ...
  void sendReport() {
    Date nextDay = new Date(previousEnd.getYear(),
      previousEnd.getMonth(), previousEnd.getDate() + 1);
    // ...
  }
}

class Report {
  // ...
  void sendReport() {
    Date newStart = nextDay(previousEnd);
    // ...
  }
  private static Date nextDay(Date arg) {
    return new Date(arg.getYear(), arg.getMonth(), arg.getDate() + 1);
  }
}

class Range {
  private int low, high;
  boolean includes(int arg) {
    return arg >= low && arg <= high;
  }
}

class Range {
  private int low, high;
  boolean includes(int arg) {
    return arg >= getLow() && arg <= getHigh();
  }
  int getLow() {
    return low;
  }
  int getHigh() {
    return high;
  }
}

String[] row = new String[2];
row[0] = "Liverpool";
row[1] = "15";

Performance row = new Performance();
row.setName("Liverpool");
row.setWins("15");

class Person {
  public String name;
}

class Person {
  private String name;

public String getName() {
    return name;
  }
  public void setName(String arg) {
    name = arg;
  }
}

double potentialEnergy(double mass, double height) {
  return mass * height * 9.81;
}

static final double GRAVITATIONAL_CONSTANT = 9.81;

double potentialEnergy(double mass, double height) {
  return mass * height * GRAVITATIONAL_CONSTANT;
}

double disabilityAmount() {
  if (seniority < 2) {
    return 0;
  }
  if (monthsDisabled > 12) {
    return 0;
  }
  if (isPartTime) {
    return 0;
  }
  // Compute the disability amount.
  // ...
}

double disabilityAmount() {
  if (isNotEligibleForDisability()) {
    return 0;
  }
  // Compute the disability amount.
  // ...
}

if (isSpecialDeal()) {
  total = price * 0.95;
  send();
}
else {
  total = price * 0.98;
  send();
}

if (isSpecialDeal()) {
  total = price * 0.95;
}
else {
  total = price * 0.98;
}
send();

if (date.before(SUMMER_START) || date.after(SUMMER_END)) {
  charge = quantity * winterRate + winterServiceCharge;
}
else {
  charge = quantity * summerRate;
}

if (isSummer(date)) {
  charge = summerCharge(quantity);
}
else {
  charge = winterCharge(quantity);
}

class Bird {
  // ...
  double getSpeed() {
    switch (type) {
      case EUROPEAN:
        return getBaseSpeed();
      case AFRICAN:
        return getBaseSpeed() - getLoadFactor() * numberOfCoconuts;
      case NORWEGIAN_BLUE:
        return (isNailed) ? 0 : getBaseSpeed(voltage);
    }
    throw new RuntimeException("Should be unreachable");
  }
}

abstract class Bird {
  // ...
  abstract double getSpeed();
}

class European extends Bird {
  double getSpeed() {
    return getBaseSpeed();
  }
}
class African extends Bird {
  double getSpeed() {
    return getBaseSpeed() - getLoadFactor() * numberOfCoconuts;
  }
}
class NorwegianBlue extends Bird {
  double getSpeed() {
    return (isNailed) ? 0 : getBaseSpeed(voltage);
  }
}

// Somewhere in client code
speed = bird.getSpeed();

String foundMiscreant(String[] people){
    String found = "";
    for (int i = 0; i < people.length; i++) {
        if (found.equals("")) {
            if (people[i].equals ("John")){
                sendAlert();
                found = "John";
            }
        }
    }
    return found;
}

String foundMiscreant(String[] people){
    for (int i = 0; i < people.length; i++) {
        if (found.equals("")) {
            if (people[i].equals ("John")){
                sendAlert();
                return "John";
            }
        }
    }
    return "";
}

public double getPayAmount() {
  double result;
  if (isDead){
    result = deadAmount();
  }
  else {
    if (isSeparated){
      result = separatedAmount();
    }
    else {
      if (isRetired){
        result = retiredAmount();
      }
      else{
        result = normalPayAmount();
      }
    }
  }
  return result;
}

public double getPayAmount() {
  if (isDead){
    return deadAmount();
  }
  if (isSeparated){
    return separatedAmount();
  }
  if (isRetired){
    return retiredAmount();
  }
  return normalPayAmount();
}

if (customer == null) {
  plan = BillingPlan.basic();
}
else {
  plan = customer.getPlan();
}

class NullCustomer extends Customer {
  boolean isNull() {
    return true;
  }
  Plan getPlan() {
    return new NullPlan();
  }
  // Some other NULL functionality.
}

// Replace null values with Null-object.
customer = (order.customer != null) ?
  order.customer : new NullCustomer();

// Use Null-object as if it's normal subclass.
plan = customer.getPlan();

double getExpenseLimit() {
  // Should have either expense limit or
  // a primary project.
  return (expenseLimit != NULL_EXPENSE) ?
    expenseLimit :
    primaryProject.getMemberExpenseLimit();
}

double getExpenseLimit() {
  Assert.isTrue(expenseLimit != NULL_EXPENSE || primaryProject != null);

return (expenseLimit != NULL_EXPENSE) ?
    expenseLimit:
    primaryProject.getMemberExpenseLimit();
}

int low = daysTempRange.getLow();
int high = daysTempRange.getHigh();
boolean withinPlan = plan.withinRange(low, high);

boolean withinPlan = plan.withinRange(daysTempRange);

void setValue(String name, int value) {
  if (name.equals("height")) {
    height = value;
    return;
  }
  if (name.equals("width")) {
    width = value;
    return;
  }
  Assert.shouldNeverReachHere();
}

void setHeight(int arg) {
  height = arg;
}
void setWidth(int arg) {
  width = arg;
}

int basePrice = quantity * itemPrice;
double seasonDiscount = this.getSeasonalDiscount();
double fees = this.getFees();
double finalPrice = discountedPrice(basePrice, seasonDiscount, fees);

int basePrice = quantity * itemPrice;
double finalPrice = discountedPrice(basePrice);

class Employee {
  Employee(int type) {
    this.type = type;
  }
  // ...
}

class Employee {
  static Employee create(int type) {
    employee = new Employee(type);
    // do some heavy lifting.
    return employee;
  }
  // ...
}

int withdraw(int amount) {
  if (amount > _balance) {
    return -1;
  }
  else {
    balance -= amount;
    return 0;
  }
}

void withdraw(int amount) throws BalanceException {
  if (amount > _balance) {
    throw new BalanceException();
  }
  balance -= amount;
}

double getValueForPeriod(int periodNumber) {
  try {
    return values[periodNumber];
  } catch (ArrayIndexOutOfBoundsException e) {
    return 0;
  }
}

double getValueForPeriod(int periodNumber) {
  if (periodNumber >= values.length) {
    return 0;
  }
  return values[periodNumber];
}

class Manager extends Employee {
  public Manager(String name, String id, int grade) {
    this.name = name;
    this.id = id;
    this.grade = grade;
  }
  // ...
}

class Manager extends Employee {
  public Manager(String name, String id, int grade) {
    super(name, id);
    this.grade = grade;
  }
  // ...
}