///////////////////// 原始代码 /////////////////////
void printOwing() {
Enumeration e = _orders.elements();
double outstanding = 0.0;

// print banner
System.out.println("***************************");
System.out.println("******** Custor Owes ******");
System.out.println("***************************");

// calculate outstanding
while (e.hasMoreElements()) {
Order each = (Order) e.nextElement();
outstanding += each.getAmount();
}

// print details
System.out.println("name:" + _name);
System.out.println("amount" + outstanding);
}

///////////////////// 重构后 /////////////////////
void printBanner() {
System.out.println("***************************");
System.out.println("******** Custor Owes ******");
System.out.println("***************************");
}

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

double getOutstanding() {
Enumeration e = _orders.elements();
double outstanding = 0.0;

while (e.hasMoreElements()) {
Order each = (Order) e.nextElement();
outstanding += each.getAmount();
}

return outstanding;
}

void printOwing() {
printBanner();
double outstanding = getOutstanding();
printDetails(outstanding);
}

///////////////// 重构前 /////////////////
// 1
public User getUser(String username, String telephone, String email);
// 2
public void postBlog(String title, String summary, String keywords, String content, String category, long authorId);

///////////////// 重构后 /////////////////
// 考虑函数是否职责单一，是否能通过拆分成多个函数的方式来减少参数。
public User getUserByUsername(String username);
public User getUserByTelephone(String telephone);
public User getUserByEmail(String email);

// 将函数的参数封装成对象
public class Blog {
private String title;
private String summary;
private String keywords;
private Strint content;
private String category;
private long authorId;
}
public void postBlog(Blog blog);

///////////////// 重构前 /////////////////
if (date.after(SUMMER_START) && date.before(SUMMER_END)) {
// ...
} else {
// ...
}

///////////////// 重构后 /////////////////
// 引入解释性变量后逻辑更加清晰
boolean isSummer = date.after(SUMMER_START)&&date.before(SUMMER_END);
if (isSummer) {
// ...
} else {
// ...
}

// 重构前的代码
public List<String> matchStrings(List<String> strList,String substr) {
List<String> matchedStrings = new ArrayList<>();
if (strList != null && substr != null) {
for (String str : strList) {
if (str != null) {
if (str.contains(substr)) {
matchedStrings.add(str);
}
}
}
}
return matchedStrings;
}

// 重构后的代码：先执行判空逻辑，再执行正常逻辑
public List<String> matchStrings(List<String> strList,String substr) {
if (strList == null || substr == null) { //先判空
return Collections.emptyList();
}

List<String> matchedStrings = new ArrayList<>();
for (String str : strList) {
if (str != null && str.contains(substr)) {
matchedStrings.add(str);
}
}
return matchedStrings;
}

public class OrderService {
public double discount(Order order) {
double discount = 0.0;
OrderType type = order.getType();
if (type.equals(OrderType.NORMAL)) { // 普通订单
//...省略折扣计算算法代码
} else if (type.equals(OrderType.GROUPON)) { // 团购订单
//...省略折扣计算算法代码
} else if (type.equals(OrderType.PROMOTION)) { // 促销订单
//...省略折扣计算算法代码
}
return discount;
}
}

// 定义策略接口
public interface DiscountStrategy {
double calDiscount(Order order);
}

// 具体策略实现
// 省略NormalDiscountStrategy、GrouponDiscountStrategy、PromotionDiscountStrategy类代码...

// 建立策略工厂
public class DiscountStrategyFactory {
private static final Map<OrderType, DiscountStrategy> strategies = new HashMap<>();

static {
strategies.put(OrderType.NORMAL, new NormalDiscountStrategy());
strategies.put(OrderType.GROUPON, new GrouponDiscountStrategy());
strategies.put(OrderType.PROMOTION, new PromotionDiscountStrategy());
}

public static DiscountStrategy getDiscountStrategy(OrderType type) {
return strategies.get(type);
}
}

// 策略的使用
public class OrderService {
public double discount(Order order) {
OrderType type = order.getType();
DiscountStrategy discountStrategy = DiscountStrategyFactory.getDiscountStrategy(type);
return discountStrategy.calDiscount(order);
}
}