Java设计模式---Strategy策略模式

参考于 :

　　大话设计模式

　　马士兵设计模式视频

　　

 

 

1.场景介绍

　　购物网站上有一个产品，有三个字段，档次，价格，重量。

　　有些同学喜欢轻的，有些手头紧，想要便宜的，有些喜欢档次高的。

　　那么我们为了提高网站用户体验，必须给六个按钮，按照价格升序降序，按照档次升序降序，按照重量升序降序。

　（这里只是打个比方，好像一般遇到这种情况是用lucenc）

2.不用策略模式

package com.dingyu;

import java.util.arrays;

/**
 * 产品类，这里为了代码代码尽可能的少，set get方法没加
 * comparable接口中有一个compareto方法,这个方法进行两个对象比较
 * arrays.sort内部方法用到了这个compareto方法
 * 这样以后只要我的类实现了comparable接口，排序的代码可以通用（arrays.sort()）去排序，可以自定义比较规则，
 * 
 * @author dingyu
 *
 */
public class product implements comparable<product> {
    private double quality;
    private double price;
    private int weight;

    public product(double quality, double price, int weight) {
        this.quality = quality;
        this.price = price;
        this.weight = weight;
    }
    
    @override
    public int compareto(product product) {
        if (this.price > product.price)
            return 1;
        else if (this.price == product.price)
            return 0;
        else
            return -1;             
    }

    @override
    public string tostring() {
        return "价格 " + price + " 重量：" + weight + " 档次：" + quality;
    }

    public static void main(string[] args) {
        product[] people = { new product(2, 500, 50), new product(3, 1000, 60), new product(1, 200, 70) };
        arrays.sort(people);
        for (int i = 0; i < people.length; i++) {
            system.out.println(people[i]);
        }
    }
}

　　jdk 源码:

 　　缺点：把compareto逻辑写死了，如果要改，需要修改compareto里的逻辑。违反开闭原则。

3.使用策略模式

　　使用一个接口，每个策略都实现这个接口

package com.dingyu;

public interface comparator<t> {
    public int compare(t t1,t t2);
}

package com.dingyu;

public class compareheight implements comparator<product> {

    @override
    public int compare(product t1, product t2) {

        if (t1.getprice() > t2.getprice())
            return 1;
        else if (t1.getprice() == t2.getprice())
            return 0;
        else
            return -1;
    }

}

package com.dingyu;

public class comparequnatity implements comparator<product>{

    @override
    public int compare(product t1, product t2) {
        if (t1.getquality() > t2.getquality())
            return 1;
        else if (t1.getquality() == t2.getquality())
            return 0;
        else
            return -1;
    }

}

package com.dingyu;

public class compareweight implements comparator<product> {

    @override
    public int compare(product t1, product t2) {
        if (t1.getweight() > t2.getweight())
            return 1;
        else if (t1.getweight() == t2.getweight())
            return 0;
        else
            return -1;
    }

}

package com.dingyu;

import java.util.arrays;

/**
 * 产品类，这里为了代码代码尽可能的少，set get方法没加 comparable接口中有一个compareto方法,这个方法进行两个对象比较
 * arrays.sort内部方法用到了这个compareto方法
 * 这样以后只要我的类实现了comparable接口，排序的代码可以通用（arrays.sort()）去排序，可以自定义比较规则，
 * 
 * @author dingyu
 *
 */
public class product implements comparable<product> {
    private double quality;
    private double price;
    private int weight;
    private static comparator<product> comparator;

    public product(double quality, double price, int weight) {
        this.quality = quality;
        this.price = price;
        this.weight = weight;
    }

    public double getquality() {
        return quality;
    }

    public void setquality(double quality) {
        this.quality = quality;
    }

    public double getprice() {
        return price;
    }

    public void setprice(double price) {
        this.price = price;
    }

    public int getweight() {
        return weight;
    }

    public void setweight(int weight) {
        this.weight = weight;
    }

    public static comparator<product> getcomparator() {
        return comparator;
    }

    public static void setcomparator(comparator<product> comparator) {
        product.comparator = comparator;
    }

    @override
    public int compareto(product product) {
        return comparator.compare(this, product);
    }

    @override
    public string tostring() {
        return "价格 " + price + " 重量：" + weight + " 档次：" + quality;
    }

    public static void main(string[] args) {
        product[] products = { new product(2, 500, 50), new product(3, 1000, 60), new product(1, 200, 70) };
        product.setcomparator(new compareheight());
        arrays.sort(products);
        for (int i = 0; i < people.length; i++) {
            system.out.println(people[i]);
        }
    }
}