重构第一例

定义:在不改变代码外在行为的前提下，对代码做出修改，以改进程序内部结构。

 

重构第一例。

 

Movie:

package refactoring;



public class Movie {

	public static final int CHILDRENS = 2;
	public static final int REGULAR = 0;
	public static final int NEW_RELEASE = 1;
	
	private String title;
//	private int priceCode;
	private Price price;
	
	public Movie(String title, int priceCode) {
		this.title = title;
//		this.priceCode = priceCode;
		setPriceCode(priceCode); // self encapsulate field
	}
	
	public int getPriceCode() {
//		return priceCode;
		return price.getPriceCode();
	}
	
	public void setPriceCode(int priceCode) {
//		this.priceCode = priceCode;
		switch(priceCode) {
		case REGULAR:
			price = new RegularPrice();
			break;
		case CHILDRENS:
			price = new ChildrensPrice();
			break;
		case NEW_RELEASE:
			price = new NewReleasePrice();
			break;
		default:
			throw new IllegalArgumentException("Incorrect Price Code");
		}
	}
	
	public double getCharge(int daysRented) {
		return price.getCharge(daysRented);
	}
	
	public String getTitle() {
		return title;
	}
	
	public int getFrequentRenterPoints(int daysRented) {
		return price.getFrequentRenterPoints(daysRented);
	}
}

 

2.Customer:

 

package refactoring;

import java.util.Enumeration;
import java.util.Vector;

public class Customer {
	
	private String name;
	private Vector<Rental> rentals = new Vector<Rental>();
	
	public Customer(String name) {
		this.name = name;
	}
	
	public void addRental(Rental rental) {
		this.rentals.add(rental);
	}
	
	public String getName() {
		return this.name;
	}
	
	public String statement() {
		Enumeration<Rental> rens = this.rentals.elements();
		String result = "Rental Record for " + getName() + "\n";
		while(rens.hasMoreElements()) {
			Rental ren = rens.nextElement();
			// replace temp with query
//			double thisAmount = ren.getCharge(); // 就函数的引用点ren.getCharge();
			// 在每次循环的时候 frequentRenterPoints已经有一个初始值 所以此处直接进行一个 附添赋值操作 
			
			result += "\t" + ren.getMovie().getPriceCode() + "\t" + ren.getCharge() + "\t";
		}
		
		// 共金额
		result += "Amount owed is " + getTotalCharge() + "\n";
		// 总积分
		result += "You earned " + getTotalFrequentRenterPoints() + " frequent renter points";
		return result;
	}
	
	// query method (replace temp with query)
	private double getTotalCharge() {
		double result = 0;
		Enumeration<Rental> rens = rentals.elements();
		while(rens.hasMoreElements()) {
			Rental rental = (Rental) rens.nextElement();
			result += rental.getCharge();
		}
		return result;
	}
	
	private int getTotalFrequentRenterPoints() {
		int result = 0;
		Enumeration<Rental> rens = rentals.elements();
		while(rens.hasMoreElements()) {
			Rental rental = (Rental) rens.nextElement();
			result += rental.getFrequentRenterPoints();
		}
		return result;
	}
}

 

 

3.Rental:

package refactoring;

/**
 * 租赁实体
 * @author zhy
 *
 */
public class Rental {

	private Movie movie;
	private int daysRented;
	
	public Rental(Movie movie, int daysRented) {
		this.movie = movie;
		this.daysRented = daysRented;
	}

	public Movie getMovie() {
		return movie;
	}

	public int getDaysRented() {
		return daysRented;
	}
	
	// 付的总金额
	public double getCharge() {
		return movie.getCharge(daysRented);
	}
	
	// 客户的积分总和
	public int getFrequentRenterPoints() {
		return movie.getFrequentRenterPoints(daysRented);
	}
}

 

 

4.Price:

package refactoring;

public abstract class Price {
	
	abstract int getPriceCode();
	
	//replace Conditional with Polymorphism
	abstract double getCharge(int daysRented);
	
	public int getFrequentRenterPoints(int daysRented) {
		return 1;
	}
}

 

 

5.ChildrensPrice

package refactoring;

public class ChildrensPrice extends Price {

	@Override
	int getPriceCode() {
		return Movie.CHILDRENS;
	}

	public double getCharge(int daysRented) {
		double result = 1.5;
		if(daysRented > 3) {
			result = (daysRented - 3) * 1.5;
		}
		return result;
	}
}

 

 

6.NewReleasePrice

package refactoring;


public class NewReleasePrice extends Price {

	@Override
	int getPriceCode() {
		return Movie.NEW_RELEASE;
	}

	public double getCharge(int daysRented) {
		return daysRented * 3;
	}
	
	public int getFrequentRenterPoints(int daysRented) {
		return daysRented > 1 ? 2 : 1;
	}
}

 

 

7.RegularPrice:

package refactoring;

public class RegularPrice extends Price {

	@Override
	int getPriceCode() {
		return Movie.REGULAR;
	}

	public double getCharge(int daysRented) {
		double result = 2;
		if(daysRented > 2) {
			result += (daysRented - 2) * 1.5;
		}
		return result;
	}
}