Strategy Pattern-鸭子行为的封装

鸭子(Duck)类，不同的鸭子具有不同的叫和飞的行为，同时要便于产生新的鸭子对象，可为鸭子添加新的行为，易于维护，动态设置行为。

不同鸭子的行为：

RedHeadDuck：红头鸭，可以用翅膀飞，呱呱叫。

RubberDuck：橡皮鸭，不会飞，吱吱叫。

ModelDuck：模型鸭，不会飞，呱呱叫。

DecoyDuck：诱饵鸭，不会飞，不会叫。

MallardDuck：野鸭，会用翅膀飞，呱呱叫。

设计原则：

1、封装变化

2、针对接口编程，而不是针对实现编程。

3、多用组合、少用继承

测试类

package com.test;

import com.duck.DecoyDuck;
import com.duck.MallardDuck;
import com.duck.ModelDuck;
import com.duck.RubberDuck;
import com.fly.FlyRocketPowered;

public class MiniDuckSimulator {

	public static void main(String[] args) {
		MallardDuck mallard = new MallardDuck();  
        RubberDuck  rubberDuckie = new RubberDuck();  
        DecoyDuck   decoy = new DecoyDuck();  
        ModelDuck   model = new ModelDuck();  
  
        mallard.display();
        mallard.performQuack(); 
        mallard.performFly();
      
        rubberDuckie.display();
        rubberDuckie.performQuack(); 
        rubberDuckie.performFly();
        
        decoy.display();
        decoy.performQuack();  
        decoy.performFly();
     
        model.display();
        model.performQuack();
        model.performFly();   
        model.setFlyBehavior(new FlyRocketPowered());  
        model.performFly();  
/*
I'm a real Mallard duck.
Quack
I'm flying!!
I'm a rubber duckie.
Squeak
I can't fly
I'm a duck Decoy.
<< Silence >>
I can't fly
I'm a model duck.
Quack
I can't fly
I'm flying with a rocket
 */
	}
}

鸭子超类与各种鸭子类

Duck

package com.duck;

import com.fly.FlyBehavior;
import com.quack.QuackBehavior;

/**
 * 鸭子抽象类
 * */
public abstract class Duck {
	//行为由接口组合而来，而不是继承.不同的鸭子行为各不相同
	FlyBehavior flyBehavior;
	QuackBehavior quackBehavior;
	
	public Duck() {
		
	}
	//行为动态设置
	public void setFlyBehavior(FlyBehavior fb) {
		flyBehavior = fb;
	}

	public void setQuackBehavior(QuackBehavior qb) {
		quackBehavior = qb;
	}
	
	abstract void display();   //不同鸭子长相不同
	//行为委托给具体的行为类处理
	public void performFly()
	{
		flyBehavior.fly();
	}
	
	public void performQuack() {
		quackBehavior.quack();
	}
	
	public void swim() {//所有的鸭子都会浮水
		System.out.println("All ducks float,even decoys!");
	}
}

DecoyDuck

package com.duck;

import com.fly.FlyNoWay;
import com.quack.MuteQuack;
/**
 * 诱饵鸭，不会飞，不会叫
 * */
public class DecoyDuck extends Duck {

	public DecoyDuck() {  
        setFlyBehavior(new FlyNoWay());  
        setQuackBehavior(new MuteQuack());  
    }  
    public void display() {  
        System.out.println("I'm a duck Decoy.");  
    }  

}

MallardDuck

package com.duck;

import com.fly.FlyWithWings;
import com.quack.Quack;
/**
 * 野鸭，会用翅膀飞，呱呱叫
 * */
public class MallardDuck extends Duck {

	public MallardDuck() {  
        quackBehavior = new Quack();  
        flyBehavior = new FlyWithWings();  
    }  
   
    public void display() {  
        System.out.println("I'm a real Mallard duck.");  
    }  

}

ModelDuck

package com.duck;

import com.fly.FlyNoWay;
import com.quack.Quack;
/**
 * 模型鸭，不会飞，呱呱叫
 * */
public class ModelDuck extends Duck {

	public ModelDuck() {  
        flyBehavior = new FlyNoWay();  
        quackBehavior = new Quack();  
    }  
  
    public void display() {  
        System.out.println("I'm a model duck.");  
    }  

}

RedHeadDuck

package com.duck;

import com.fly.FlyWithWings;
import com.quack.Quack;
/**
 * 红头鸭，可以用翅膀飞，呱呱叫
 * */
public class RedHeadDuck extends Duck {

	public RedHeadDuck() {  
        flyBehavior = new FlyWithWings();  
        quackBehavior = new Quack();  
    }  
	@Override
	void display() {
		// TODO Auto-generated method stub
		System.out.println("I'm a real Red Headed duck.");
	}

}

RubberDuck

package com.duck;

import com.fly.FlyNoWay;
import com.quack.Squeak;
/**
 * 橡皮鸭，不会飞，吱吱叫
 * */
public class RubberDuck extends Duck {

	public RubberDuck() {  
        flyBehavior = new FlyNoWay();  
        quackBehavior = new Squeak();  
    }  
   
    public void display() {  
        System.out.println("I'm a rubber duckie.");  
    }  

}

飞行为接口与各种具体的飞行为类

FlyBehavior

package com.fly;
/**
 * 鸭子飞行的行为接口
 */
public interface FlyBehavior {
	public void fly();
}

FlyNoWay

package com.fly;
/**
 * 不会飞
 */
public class FlyNoWay implements FlyBehavior {

	@Override
	public void fly() {
		// TODO Auto-generated method stub
		System.out.println("I can't fly");  
	}

}

FlyRocketPowered

package com.fly;
/**
 * 用火箭助力飞
 */
public class FlyRocketPowered implements FlyBehavior{

	@Override
	public void fly() {
		// TODO Auto-generated method stub
		System.out.println("I'm flying with a rocket"); 
	}

}

FlyWithWings

package com.fly;
/**
 * 用翅膀飞
 */
public class FlyWithWings implements FlyBehavior {

	@Override
	public void fly() {
		// TODO Auto-generated method stub
		System.out.println("I'm flying!!"); 
	}

}

叫行为接口与各种具体的叫行为类

QuackBehavior

package com.quack;
/**
 *鸭子叫的行为接口
 */
public interface QuackBehavior {
	public void quack();
}

FakeQuack

package com.quack;
/**
 * 假叫
 * */
public class FakeQuack implements QuackBehavior {

	@Override
	public void quack() {
		// TODO Auto-generated method stub
		System.out.println("Qwak");
	}

}

MuteQuack

package com.quack;
/**
 * 不会叫
 * */
public class MuteQuack implements QuackBehavior {

	@Override
	public void quack() {
		// TODO Auto-generated method stub
		System.out.println("<< Silence >>");
	}

}

Quack

package com.quack;
/**
 * 呱呱叫
 * */
public class Quack implements QuackBehavior {

	@Override
	public void quack() {
		// TODO Auto-generated method stub
		System.out.println("Quack"); 
	}

}

Squeak

package com.quack;
/**
 * 吱吱叫
 * */
public class Squeak implements QuackBehavior {

	@Override
	public void quack() {
		// TODO Auto-generated method stub
		System.out.println("Squeak");  
	}

}