“策略模式”原来如此简单

一、策略模式简介

1、定义

 2、使用场景

3、优缺点

3、UML类图

 

​

 二、策略模式实现

1、策略角色

package com.mfc.design.策略模式;

/**
 * @author MouFangCai
 * @date 2019/10/11 11:28
 */
public abstract class Strategy {

    // 算法方法
    public abstract void algorithmInterface();
}

2、具体策略角色

package com.mfc.design.策略模式;

/**
 * @author MouFangCai
 * @date 2019/10/11 11:31
 */
public class ConcreteStrategyA extends Strategy {
    @Override
    public void algorithmInterface() {
        System.out.println("这是算法A");
    }
}

3、 Context上下文

package com.mfc.design.策略模式;

/**
 * @author MouFangCai
 * @date 2019/10/11 11:32
 */
public class Context {

    Strategy strategy;

    public Context (Strategy strategy) {
        // 初始化时，传入具体的策略对象
        this.strategy = strategy;
    }

    // 上下文接口
    public void ContextInterface() {
        // 根据具体的策略对象，调用就其算法的方法
        strategy.algorithmInterface();
    }
}

　4、Client客户端

package com.mfc.design.策略模式;

/**
 * @author MouFangCai
 * @date 2019/10/11 11:36
 */
public class Client_Strategy {


    public static void main(String[] args) {
        doStrategy("A");
        doStrategy("B");
        doStrategy("C");
    }

    public static void doStrategy(String options){
        Context context = null;
        switch (options){
            case "A":
                context = new Context(new ConcreteStrategyA());
                context.ContextInterface();
                break;
            case "B":
                context = new Context(new ConcreteStrategyB());
                context.ContextInterface();
                break;
            case "C":
                context = new Context(new ConcreteStrategyC());
                context.ContextInterface();
                break;
        }
    }
}

运行结果如下：

5、分析

三、策略模式与简单工厂结合

1、改造后的context

package com.mfc.design.策略模式;

/**
 * @author MouFangCai
 * @date 2019/10/11 11:32
 */
public class Context_Factory {


    Strategy strategy = null;

    public Context_Factory(String options) {
        // 初始化时，根据客户端不同的选择，实例化具体的策略对象
        switch (options){
            case "A":
                strategy = new ConcreteStrategyA();
                break;
            case "B":
                strategy = new ConcreteStrategyB();
                break;
            case "C":
                strategy = new ConcreteStrategyC();
                break;
        }
    }

    // 上下文接口
    public void ContextInterface() {
        // 根据具体的策略对象，调用就其算法的方法
        strategy.algorithmInterface();
    }
}

2、改造后的客户端

package com.mfc.design.策略模式;

/**
 * @author MouFangCai
 * @date 2019/10/11 11:36
 */
public class Client_Strategy_Factory {


    public static void main(String[] args) {
        String options =  "A";
        Context_Factory a = new Context_Factory(options);
        a.ContextInterface();
    }

}