java - 如何实现策略设计模式

Question

谁能告诉我们如何在下面的代码中实现策略设计模式。我已经浏览了各种链接，但对实施它并不完全清楚。问题是：使用策略设计模式计算点数并以 PDF 或 HTML 格式显示报告。下面是已经可用的代码。Customer、Movie 和 Rental 是已经创建的类：

1. 客户.java

    public class Customer {
    private String _name;
    private Vector _rentals = new Vector();
    public Customer(String name) {
    _name = name;
    };
   
    public void addRental(Rental arg) {
    _rentals.addElement(arg);
    }
   
    public String getName() {
    return _name;
    }
   
   public static void main(String[] args) {
   
    Customer c = new Customer("ABC");
    Movie m = new Movie("Title", 1);
    Rental r = new Rental(m, 10);
    c.addRental(r);
    // Rental calculation
    String s = c.statement();
    System.out.println("s: " + s);
   }
        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();
   
        // determine amounts for each line
        switch (each.getMovie().getPriceCode()) {
   
        case Movie.REGULAR:
            thisAmount += 2;
            if (each.getDaysRented() > 2)
                thisAmount += (each.getDaysRented() - 2) * 1.5;
            break;
   
        case Movie.NEW_RELEASE:
            thisAmount += each.getDaysRented() * 3;
            break;
   
        case Movie.CHILDRENS:
            thisAmount += 1.5;
            if (each.getDaysRented() > 3)
                thisAmount += (each.getDaysRented() - 3) * 1.5;
            break;
        } // add frequent
            // renter points
        frequentRenterPoints++;
   
        // add bonus for a two day new release rental
        if ((each.getMovie().getPriceCode() == Movie.NEW_RELEASE) && each.getDaysRented() > 1)
            frequentRenterPoints++;
   
        // show figures for this rental
        result += "\t" + each.getMovie().getTitle() + "\t" + String.valueOf(thisAmount) + "\n";
        totalAmount += thisAmount;
    }
   
    // add footer lines
    result += "Amount owed is " + String.valueOf(totalAmount) + "\n";
    result += "You earned " + String.valueOf(frequentRenterPoints) + " frequent renter points";
    return result;
    }
    }
   

2. 电影.java

   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;
   
    public Movie(String title, int priceCode) {
   _title = title;
   _priceCode = priceCode;
   }
   public int getPriceCode() {
       return _priceCode;
   }
   
   public void setPriceCode(int arg) {
   _priceCode = arg;
   }
   public String getTitle() {
   return _title;
   };
   }
   

3. 出租.java

   public class Rental {
       private Movie _movie;
   private int _daysRented;
   public Rental(Movie movie, int daysRented) {
       _movie = movie;
   _daysRented = daysRented;
   }
   public int getDaysRented() {
       return _daysRented;
   }
       public Movie getMovie() {
       return _movie;
   }
   }
   

标签： javadesign-patterns

Answer 1

您的任务是“使用策略设计模式以 PDF 或 HTML 格式显示报告”，因此将在此处应用策略。在显示报告之前，您应该拥有所有计算数据（保持工作已完成），然后只需传递数据并选择适当的报告类型。

public interface IReport 
{
    public void printReport(String data);
}

public class ReportHTML implements IReport
{
    @Override
    public void printReport(String data) {
        System.out.println("Html Report with data="+data);  
    }
}

public class ReportPDF implements IReport{
    @Override
    public void printReport(String data) {
        System.out.println("PDF Report with data="+data);   
    }
}

public class Test {
    public static void main(String[] args)
    {
        //do whatever computation concerning business logic
        //after for print pass computed data and chose report type as needed
        IReport ir = new ReportHTML();
        ir.printReport("[Customers, Movie, Rental]");
        ir = new ReportPDF();
        ir.printReport("[Customers, Movie, Rental]");
    }
}

输出：

Html Report with data=[Customers, Movie, Rental]
PDF Report with data=[Customers, Movie, Rental]