23种设计模式----命令模式----行为型模式

2023年4月9日 300次阅读 来源: 算法小白

命令模式

  • 1.什么是命令模式
  • 2.命令模式的角色
  • 3.模式图
  • 4.例子
    • 4.1例子背景
    • 4.2 结构图
    • 4.3 命令接口
    • 4.4 命令抽象方法
    • 4.5 实现的命令
    • 4.6 命令的集合
    • 4.7 抽象的持有者
    • 4.8 实现的持有者
    • 4.9 命令的发动者
    • 4.10 命令的请求者
    • 4.11 结果
  • 5.总结
    • 5.1 命令的享元工厂
    • 5.2 执行者的享元工厂
      • 5.2.1抽象的命令的集合：
      • 5.2.2具体的命令的集合
      • 5.2.3 抽象的命令的发动者
      • 5.2.4 具体的命令的发动者
    • 5.2.5 调用者
      • 5.2.6 结果
      • 5.2.7 说明

23种设计模式

1.什么是命令模式

命令就是需要自己命令的对象进行的操作。

首先，分为两个方面：
对于命令方，命令是最小单位。
对于被命令方，命令是最大单位。

其次：
命令有发出角色，有执行角色。
同时：
命令有发出时间，有执行时间。

等等。

所以，命令模式主要解决就是把一系列复杂的操作，（相对不变）封装起来，等到需要再次调用时，不需要创建，只需要调用即可。
命令模式大大的降低了使用者的条件，但是却可能变相的增加提供者的条件。

举个例子：使用接口封装的服务，可能对于提供者来说比较容易实现，但是对于调用者来说，调用可能比较困难。
而使用命令模式，可以大大的较低调用者的使用难度，相应的，提供者的提供难度将会增加。

2.命令模式的角色

抽象的命令：定义命令需要实现什么操作
实现的命令 ：抽象的命令进行实现
命令的执行者：命令将由这个角色进行执行
命令的请求者：发起命令的角色
命令的发动者：决定何时执行命令

一般来说：命令的请求者持有命令，实现的命令持有命令的执行者，命令的执行者决定时间。

3.模式图

实现
持有
持有
决定 实现的命令 抽象的命令 命令的执行者 命令的请求者 命令的发动者

从上图可以看出，命令模式几乎完全解耦了调用者和提供者的关系。
调用者几乎不需要了解操作是如何实现的。
调用者只需要发起命令的请求。

4.例子

实例源码下载传送门(资源暂未审核，通过后及时增加)

4.1例子背景

现在生活条件上升，很多人都有了自己的小汽车，所以，很多人都会开车。
下面的例子就是关于如何开车。
首先，开车的步骤大家都知道。
举一个例子：起步：
起步需要：

  • 系安全带
  • 左转向灯
  • 左转向
  • 刹车
  • 点火
  • 离合
  • 挂挡
  • 给油
    为了简单，在本次例子中，离合就认为是踩下离合并且在合适的时间释放离合，刹车也是，给油认为是根据需要踩给油踏板。

4.2 结构图

《23种设计模式----命令模式----行为型模式》
《23种设计模式----命令模式----行为型模式》

4.3 命令接口

package order.intf;

public interface IntfCommand {

	void execute();
	
}

4.4 命令抽象方法

package order.abs;

import order.intf.IntfCommand;
import receive.abs.AbsCar;

public abstract class AbsCommand implements IntfCommand{

	protected AbsCar absCar;
	
	public AbsCommand(){
		init();
	}
	
	protected abstract void init();

	@Override
	public void execute() {
		System.out.println(this.getClass() + "\texecute\t"
				+ this);
		absCar.receive();
	}
	
}

4.5 实现的命令

package order.command;

import order.abs.AbsCommand;
import receive.component.BrakeRec;

/**
 * 
 * 刹车
 */
public class BrakeComm extends AbsCommand {

	@Override
	protected void init() {
		absCar = new BrakeRec();
		System.out.println(this.getClass() + ":" + this
				+ "\tinit\t" + absCar.getClass() + ":"
				+ absCar);
	}

}


package order.command;

import order.abs.AbsCommand;
import receive.component.ClutchRec;

/**
 * 
 * 离合
 */
public class ClutchComm extends AbsCommand {

	@Override
	protected void init() {

		absCar = new ClutchRec();
		System.out.println(this.getClass() + ":" + this
				+ "\tinit\t" + absCar.getClass() + ":"
				+ absCar);

	}

}


package order.command;

import order.abs.AbsCommand;
import receive.component.HangOutRec;

/**
 * 
 * 挂挡
 */
public class HangOutComm extends AbsCommand {

	@Override
	protected void init() {
		absCar = new HangOutRec();
		System.out.println(this.getClass() + ":" + this
				+ "\tinit\t" + absCar.getClass() + ":"
				+ absCar);
	}

}


package order.command;

import order.abs.AbsCommand;
import receive.component.IgnitionRec;

/**
 * 点火
 *
 */
public class IgnitionComm extends AbsCommand {

	@Override
	protected void init() {
		absCar = new IgnitionRec();
		System.out.println(this.getClass() + ":" + this
				+ "\tinit\t" + absCar.getClass() + ":"
				+ absCar);
	}

}


package order.command;

import order.abs.AbsCommand;
import receive.component.OilRec;

/**
 * 给油
 *
 */
public class OilComm extends AbsCommand {

	@Override
	protected void init() {
		absCar = new OilRec();
		System.out.println(this.getClass() + ":" + this
				+ "\tinit\t" + absCar.getClass() + ":"
				+ absCar);
	}

}


package order.command;

import order.abs.AbsCommand;
import receive.component.PutOutRec;

/**
 * 
 * 熄火
 */
public class PutOutComm extends AbsCommand {

	@Override
	protected void init() {
		absCar = new PutOutRec();
		System.out.println(this.getClass() + ":" + this
				+ "\tinit\t" + absCar.getClass() + ":"
				+ absCar);
	}

}


package order.command;

import order.abs.AbsCommand;
import receive.component.SteeringWheelLeftRec;

/**
 * 
 * 左打方向盘
 */
public class SteeringWheelLeftComm extends AbsCommand {

	@Override
	protected void init() {
		absCar = new SteeringWheelLeftRec();
		System.out.println(this.getClass() + ":" + this
				+ "\tinit\t" + absCar.getClass() + ":"
				+ absCar);
	}

}



package order.command;

import order.abs.AbsCommand;
import receive.component.SteeringWheelRightRec;

/**
 * 
 * 右打方向盘
 */
public class SteeringWheelRightComm extends AbsCommand {

	@Override
	protected void init() {
		absCar = new SteeringWheelRightRec();
		System.out.println(this.getClass() + ":" + this
				+ "\tinit\t" + absCar.getClass() + ":"
				+ absCar);
	}

}



package order.command;

import order.abs.AbsCommand;
import receive.component.TurnSignalLeftRec;

/**
 * 
 * 左转向灯
 */
public class TurnSignalLeftComm extends AbsCommand {

	@Override
	protected void init() {
		absCar = new TurnSignalLeftRec();
		System.out.println(this.getClass() + ":" + this
				+ "\tinit\t" + absCar.getClass() + ":"
				+ absCar);
	}

}



package order.command;

import order.abs.AbsCommand;
import receive.component.TurnSignalRightRec;

/**
 * 
 * 右转向灯
 */
public class TurnSignalRightComm extends AbsCommand {

	@Override
	protected void init() {
		absCar = new TurnSignalRightRec();
		System.out.println(this.getClass() + ":" + this
				+ "\tinit\t" + absCar.getClass() + ":"
				+ absCar);
	}

}


package order.command;

import order.abs.AbsCommand;
import receive.component.WearingSeatbeltRec;

/**
 * 
 * 系安全带
 */
public class WearingSeatbeltComm extends AbsCommand {

	@Override
	protected void init() {
		absCar = new WearingSeatbeltRec();
		System.out.println(this.getClass() + ":" + this
				+ "\tinit\t" + absCar.getClass() + ":"
				+ absCar);
	}

}

4.6 命令的集合

package order.step;

import java.util.LinkedList;
import java.util.Queue;

import order.command.BrakeComm;
import order.command.ClutchComm;
import order.command.HangOutComm;
import order.command.IgnitionComm;
import order.command.OilComm;
import order.command.SteeringWheelLeftComm;
import order.command.TurnSignalLeftComm;
import order.command.WearingSeatbeltComm;
import order.intf.IntfCommand;

/**
 * 车起步：
 * 
 * 系安全带
 * 左转向灯
 * 左转向
 * 刹车
 * 点火 
 * 离合
 * 挂挡
 * 给油
 *
 */
public class CarStart implements IntfCommand{

	private Queue<IntfCommand> step = new LinkedList<IntfCommand>();
	
	public CarStart() {
		
		init();
		
	}
	
	private void init(){
		
		step.add(new WearingSeatbeltComm());
		step.add(new TurnSignalLeftComm());
		step.add(new SteeringWheelLeftComm());
		step.add(new BrakeComm());
		step.add(new IgnitionComm());
		step.add(new ClutchComm());
		step.add(new HangOutComm());
		step.add(new OilComm());
		
		System.out.println(this.getClass().getName() + "\tinit\t"
				+ step.getClass().getName());
	}
	
	@Override
	public void execute() {
		System.out.println(this.getClass() + "\texecute\t"
				+ this);
		IntfCommand command = step.poll();
		while(command != null){
			command.execute();
			command = step.poll();
		}
		
	}


}

4.7 抽象的持有者

package receive.abs;



public abstract class AbsCar {

	
	public void receive(){
		System.out.println(this.getClass() + "\treceive\t"
				+ this);
		doReceive();
	}
	
	protected abstract void doReceive();
	
}

4.8 实现的持有者

package receive.component;

import receive.abs.AbsCar;

/**
 * 
 * 刹车
 */
public class BrakeRec extends AbsCar{

	@Override
	protected void doReceive() {
		
		System.out.println(this.getClass() + "\tdoReceive\t"
				+ this);
		System.out.println("刹车");
		
	}

}



package receive.component;

import receive.abs.AbsCar;

/**
 * 
 * 离合
 */
public class ClutchRec extends AbsCar{

	@Override
	protected void doReceive() {
		
		System.out.println(this.getClass() + "\tdoReceive\t"
				+ this);
		System.out.println("离合");
		
	}

}



package receive.component;

import receive.abs.AbsCar;

/**
 * 
 * 挂挡
 */
public class HangOutRec extends AbsCar{

	@Override
	protected void doReceive() {
		
		System.out.println(this.getClass() + "\tdoReceive\t"
				+ this);
		System.out.println("挂挡");
		
	}

}



package receive.component;

import receive.abs.AbsCar;

/**
 * 点火
 *
 */
public class IgnitionRec extends AbsCar{

	@Override
	protected void doReceive() {
		
		System.out.println(this.getClass() + "\tdoReceive\t"
				+ this);
		System.out.println("点火");
		
	}

}



package receive.component;

import receive.abs.AbsCar;

/**
 * 给油
 *
 */
public class OilRec extends AbsCar{

	@Override
	protected void doReceive() {
		
		System.out.println(this.getClass() + "\tdoReceive\t"
				+ this);
		System.out.println("给油");
		
	}

}



package receive.component;

import receive.abs.AbsCar;

/**
 * 
 * 熄火
 */
public class PutOutRec extends AbsCar{

	@Override
	protected void doReceive() {
		
		System.out.println(this.getClass() + "\tdoReceive\t"
				+ this);
		System.out.println("熄火");
		
	}

}



package receive.component;

import receive.abs.AbsCar;

/**
 * 
 * 左打方向盘
 */
public class SteeringWheelLeftRec extends AbsCar {

	@Override
	protected void doReceive() {

		System.out.println(this.getClass() + "\tdoReceive\t"
				+ this);
		System.out.println("左打方向盘");

	}

}



package receive.component;

import receive.abs.AbsCar;

/**
 * 
 * 右打方向盘
 */
public class SteeringWheelRightRec extends AbsCar{

	@Override
	protected void doReceive() {
		
		System.out.println(this.getClass() + "\tdoReceive\t"
				+ this);
		System.out.println("右打方向盘");
		
	}

}



package receive.component;

import receive.abs.AbsCar;

/**
 * 
 * 左转向灯
 */
public class TurnSignalLeftRec extends AbsCar{

	@Override
	protected void doReceive() {
		
		System.out.println(this.getClass() + "\tdoReceive\t"
				+ this);
		System.out.println("左转向灯");
		
	}

}



package receive.component;

import receive.abs.AbsCar;

/**
 * 
 * 右转向灯
 */
public class TurnSignalRightRec extends AbsCar{

	@Override
	protected void doReceive() {
		
		System.out.println(this.getClass() + "\tdoReceive\t"
				+ this);
		System.out.println("右转向灯");
		
	}

}



package receive.component;

import receive.abs.AbsCar;

/**
 * 
 * 系安全带
 */
public class WearingSeatbeltRec extends AbsCar{

	@Override
	protected void doReceive() {
		
		System.out.println(this.getClass() + "\tdoReceive\t"
				+ this);
		System.out.println("系安全带");
		
	}

}

4.9 命令的发动者

package receive.car;

import receive.abs.AbsCar;

/**
 * 车起步：
 * 
 * 系安全带 左转向灯 左转向 刹车 点火 离合 挂挡 给油
 *
 */
public class CarStart extends AbsCar {

	private order.step.CarStart carStart;

	public CarStart() {

		init();
	}

	private void init() {
		carStart = new order.step.CarStart();
		System.out.println(this.getClass() + ":" + this
				+ "\tinit\t" + carStart.getClass() + ":"
				+ carStart);
	}

	@Override
	protected void doReceive() {
		System.out.println(this.getClass().getName() + "\tdoReceive\t"
				+ this.getClass());
		carStart.execute();
	}

}

4.10 命令的请求者

package client;

import receive.car.CarStart;

public class Main {

	public static void main(String[] args) {

		System.out.println("生成命令");
		CarStart carStart = new CarStart();
		System.out.println("执行命令");
		carStart.receive();
	}

}

4.11 结果

生成命令
class order.command.WearingSeatbeltComm:order.command.WearingSeatbeltComm@1befab0	init	class receive.component.WearingSeatbeltRec:receive.component.WearingSeatbeltRec@13c5982
class order.command.TurnSignalLeftComm:order.command.TurnSignalLeftComm@c21495	init	class receive.component.TurnSignalLeftRec:receive.component.TurnSignalLeftRec@1d5550d
class order.command.SteeringWheelLeftComm:order.command.SteeringWheelLeftComm@1034bb5	init	class receive.component.SteeringWheelLeftRec:receive.component.SteeringWheelLeftRec@15f5897
class order.command.BrakeComm:order.command.BrakeComm@186d4c1	init	class receive.component.BrakeRec:receive.component.BrakeRec@f9f9d8
class order.command.IgnitionComm:order.command.IgnitionComm@87816d	init	class receive.component.IgnitionRec:receive.component.IgnitionRec@422ede
class order.command.ClutchComm:order.command.ClutchComm@93dcd	init	class receive.component.ClutchRec:receive.component.ClutchRec@b89838
class order.command.HangOutComm:order.command.HangOutComm@a83b8a	init	class receive.component.HangOutRec:receive.component.HangOutRec@dd20f6
class order.command.OilComm:order.command.OilComm@22c95b	init	class receive.component.OilRec:receive.component.OilRec@1d1acd3
order.step.CarStart	init	java.util.LinkedList
class receive.car.CarStart:receive.car.CarStart@a981ca	init	class order.step.CarStart:order.step.CarStart@8814e9
执行命令
class receive.car.CarStart	receive	receive.car.CarStart@a981ca
receive.car.CarStart	doReceive	class receive.car.CarStart
class order.step.CarStart	execute	order.step.CarStart@8814e9
class order.command.WearingSeatbeltComm	execute	order.command.WearingSeatbeltComm@1befab0
class receive.component.WearingSeatbeltRec	receive	receive.component.WearingSeatbeltRec@13c5982
class receive.component.WearingSeatbeltRec	doReceive	receive.component.WearingSeatbeltRec@13c5982
系安全带
class order.command.TurnSignalLeftComm	execute	order.command.TurnSignalLeftComm@c21495
class receive.component.TurnSignalLeftRec	receive	receive.component.TurnSignalLeftRec@1d5550d
class receive.component.TurnSignalLeftRec	doReceive	receive.component.TurnSignalLeftRec@1d5550d
左转向灯
class order.command.SteeringWheelLeftComm	execute	order.command.SteeringWheelLeftComm@1034bb5
class receive.component.SteeringWheelLeftRec	receive	receive.component.SteeringWheelLeftRec@15f5897
class receive.component.SteeringWheelLeftRec	doReceive	receive.component.SteeringWheelLeftRec@15f5897
左打方向盘
class order.command.BrakeComm	execute	order.command.BrakeComm@186d4c1
class receive.component.BrakeRec	receive	receive.component.BrakeRec@f9f9d8
class receive.component.BrakeRec	doReceive	receive.component.BrakeRec@f9f9d8
刹车
class order.command.IgnitionComm	execute	order.command.IgnitionComm@87816d
class receive.component.IgnitionRec	receive	receive.component.IgnitionRec@422ede
class receive.component.IgnitionRec	doReceive	receive.component.IgnitionRec@422ede
点火
class order.command.ClutchComm	execute	order.command.ClutchComm@93dcd
class receive.component.ClutchRec	receive	receive.component.ClutchRec@b89838
class receive.component.ClutchRec	doReceive	receive.component.ClutchRec@b89838
离合
class order.command.HangOutComm	execute	order.command.HangOutComm@a83b8a
class receive.component.HangOutRec	receive	receive.component.HangOutRec@dd20f6
class receive.component.HangOutRec	doReceive	receive.component.HangOutRec@dd20f6
挂挡
class order.command.OilComm	execute	order.command.OilComm@22c95b
class receive.component.OilRec	receive	receive.component.OilRec@1d1acd3
class receive.component.OilRec	doReceive	receive.component.OilRec@1d1acd3
给油

5.总结

可以看到上面的例子中new了非常多的对象。而且new出来的这些对象基本上都相同。
所以，能不能使用享元模式提高性能。

5.1 命令的享元工厂

package order.flyweight;

import java.util.HashMap;
import java.util.Map;

import order.abs.AbsCommand;

public class FlyWeightComm {

	private static Map<String, AbsCommand> map = new HashMap<String, AbsCommand>();
	
	private static final FlyWeightComm instance = new FlyWeightComm();
	
	private FlyWeightComm(){
		
	}
	
	public static FlyWeightComm getInstance(){
		return instance;
	}
	
	public static AbsCommand getAbsCommand(String comm){
		if(map.containsKey(comm)){
			return map.get(comm);
		} else {
			AbsCommand command = null;
			try {
				command = (AbsCommand)Class.forName("order.command."+comm).newInstance();
			} catch (InstantiationException e) {
				e.printStackTrace();
			} catch (IllegalAccessException e) {
				e.printStackTrace();
			} catch (ClassNotFoundException e) {
				e.printStackTrace();
			}
			map.put(comm, command);
			return command;
		}
	}
	
}

5.2 执行者的享元工厂

package receive.flyweight;

import java.util.HashMap;
import java.util.Map;

import receive.abs.AbsCar;

public class FlyWeightRec {

	private static Map<String, AbsCar> map = new HashMap<String, AbsCar>();
	
	private static final FlyWeightRec instance = new FlyWeightRec();
	
	private FlyWeightRec(){
		
	}
	
	public static FlyWeightRec getInstance(){
		return instance;
	}
	
	public static AbsCar getAbsCar(String recName){
		if(map.containsKey(recName)){
			return map.get(recName);
		} else {
			AbsCar absCar = null;
			try {
				absCar = (AbsCar)Class.forName("receive.component."+recName).newInstance();
			} catch (InstantiationException e) {
				e.printStackTrace();
			} catch (IllegalAccessException e) {
				e.printStackTrace();
			} catch (ClassNotFoundException e) {
				e.printStackTrace();
			}
			map.put(recName, absCar);
			return absCar;
		}
	} 
	
}

结果完全相同。

但是我们在增加一种操作：
加速：
给油、离合、挂挡、给油。
加的时候发现命令的集合这个角色的类的相似度非常的高，所以我们对命令的角色的类进行重构：抽取抽象类：

5.2.1抽象的命令的集合：

package order.step.abs;

import java.util.LinkedList;
import java.util.Queue;

import order.intf.IntfCommand;

public abstract class CarCommAbs implements IntfCommand{

	protected Queue<IntfCommand> step = new LinkedList<IntfCommand>();
	
	public CarCommAbs() {
	
		init();
		
	}
	
	protected abstract void init();
	
	@Override
	public void execute() {
		System.out.println(this.getClass() + "\texecute\t"
				+ this);
		IntfCommand command = step.poll();
		while(command != null){
			command.execute();
			command = step.poll();
		}
		
	}
	
}

5.2.2具体的命令的集合

package order.step.impl;

import order.flyweight.FlyWeightComm;
import order.step.abs.CarCommAbs;

/**
 * 车起步：
 * 
 * 系安全带
 * 左转向灯
 * 左转向
 * 刹车
 * 点火 
 * 离合
 * 挂挡
 * 给油
 *
 */
public class CarStartComm extends CarCommAbs{

	@Override
	protected void init(){
		
		step.add(FlyWeightComm.getAbsCommand("WearingSeatbeltComm"));
		step.add(FlyWeightComm.getAbsCommand("TurnSignalLeftComm"));
		step.add(FlyWeightComm.getAbsCommand("SteeringWheelLeftComm"));
		step.add(FlyWeightComm.getAbsCommand("BrakeComm"));
		step.add(FlyWeightComm.getAbsCommand("IgnitionComm"));
		step.add(FlyWeightComm.getAbsCommand("ClutchComm"));
		step.add(FlyWeightComm.getAbsCommand("HangOutComm"));
		step.add(FlyWeightComm.getAbsCommand("OilComm"));
		
		System.out.println(this.getClass().getName() + "\tinit\t"
				+ step.getClass().getName());
	}
	
}


package order.step.impl;

import order.flyweight.FlyWeightComm;
import order.step.abs.CarCommAbs;

public class CarAddComm extends CarCommAbs{

	@Override
	protected void init() {
		
		step.add(FlyWeightComm.getAbsCommand("OilComm"));
		step.add(FlyWeightComm.getAbsCommand("ClutchComm"));
		step.add(FlyWeightComm.getAbsCommand("HangOutComm"));
		step.add(FlyWeightComm.getAbsCommand("OilComm"));
		
	}

	
}

5.2.3 抽象的命令的发动者

package receive.car.abs;

import order.step.abs.CarCommAbs;
import receive.abs.AbsCar;

public abstract class CarRecAbs extends AbsCar{

	protected CarCommAbs carStart;

	public CarRecAbs() {

		init();
	}
	
	protected abstract void init(); 
	
	@Override
	protected void doReceive() {
		System.out.println(this.getClass().getName() + "\tdoReceive\t"
				+ this.getClass());
		carStart.execute();
	}

}

5.2.4 具体的命令的发动者

package receive.car.impl;

import order.step.impl.CarAddComm;
import receive.car.abs.CarRecAbs;

public class CarAddRec extends CarRecAbs{

	@Override
	protected void init() {
		carStart = new CarAddComm();
		System.out.println(this.getClass() + ":" + this
				+ "\tinit\t" + carStart.getClass() + ":"
				+ carStart);
	}

}


package receive.car.impl;

import order.step.impl.CarStartComm;
import receive.car.abs.CarRecAbs;

/**
 * 车起步：
 * 
 * 系安全带 左转向灯 左转向 刹车 点火 离合 挂挡 给油
 *
 */
public class CarStartRec extends CarRecAbs {

	@Override
	protected void init() {
		carStart = new CarStartComm();
		System.out.println(this.getClass() + ":" + this
				+ "\tinit\t" + carStart.getClass() + ":"
				+ carStart);
	}

}

5.2.5 调用者

package client;

import receive.car.impl.CarAddRec;
import receive.car.impl.CarStartRec;

public class Main {

	public static void main(String[] args) {

		System.out.println("生成命令----起步");
		CarStartRec carStart = new CarStartRec();
		System.out.println("生成命令----加速");
		CarAddRec carAddRec = new CarAddRec();
		System.out.println("执行命令----加速");
		carStart.receive();
		System.out.println("执行命令----加速");
		carAddRec.receive();
	}

}

5.2.6 结果

生成命令----起步
class order.command.WearingSeatbeltComm:order.command.WearingSeatbeltComm@c2ea3f	init	class receive.component.WearingSeatbeltRec:receive.component.WearingSeatbeltRec@a0dcd9
class order.command.TurnSignalLeftComm:order.command.TurnSignalLeftComm@b162d5	init	class receive.component.TurnSignalLeftRec:receive.component.TurnSignalLeftRec@1cfb549
class order.command.SteeringWheelLeftComm:order.command.SteeringWheelLeftComm@1820dda	init	class receive.component.SteeringWheelLeftRec:receive.component.SteeringWheelLeftRec@15b7986
class order.command.BrakeComm:order.command.BrakeComm@112f614	init	class receive.component.BrakeRec:receive.component.BrakeRec@1d9dc39
class order.command.IgnitionComm:order.command.IgnitionComm@111a3ac	init	class receive.component.IgnitionRec:receive.component.IgnitionRec@110b053
class order.command.ClutchComm:order.command.ClutchComm@19efb05	init	class receive.component.ClutchRec:receive.component.ClutchRec@723d7c
class order.command.HangOutComm:order.command.HangOutComm@a981ca	init	class receive.component.HangOutRec:receive.component.HangOutRec@8814e9
class order.command.OilComm:order.command.OilComm@743399	init	class receive.component.OilRec:receive.component.OilRec@e7b241
order.step.impl.CarStartComm	init	java.util.LinkedList
class receive.car.impl.CarStartRec:receive.car.impl.CarStartRec@167d940	init	class order.step.impl.CarStartComm:order.step.impl.CarStartComm@e83912
生成命令----加速
class receive.car.impl.CarAddRec:receive.car.impl.CarAddRec@1d8957f	init	class order.step.impl.CarAddComm:order.step.impl.CarAddComm@3ee284
执行命令----加速
class receive.car.impl.CarStartRec	receive	receive.car.impl.CarStartRec@167d940
receive.car.impl.CarStartRec	doReceive	class receive.car.impl.CarStartRec
class order.step.impl.CarStartComm	execute	order.step.impl.CarStartComm@e83912
class order.command.WearingSeatbeltComm	execute	order.command.WearingSeatbeltComm@c2ea3f
class receive.component.WearingSeatbeltRec	receive	receive.component.WearingSeatbeltRec@a0dcd9
class receive.component.WearingSeatbeltRec	doReceive	receive.component.WearingSeatbeltRec@a0dcd9
系安全带
class order.command.TurnSignalLeftComm	execute	order.command.TurnSignalLeftComm@b162d5
class receive.component.TurnSignalLeftRec	receive	receive.component.TurnSignalLeftRec@1cfb549
class receive.component.TurnSignalLeftRec	doReceive	receive.component.TurnSignalLeftRec@1cfb549
左转向灯
class order.command.SteeringWheelLeftComm	execute	order.command.SteeringWheelLeftComm@1820dda
class receive.component.SteeringWheelLeftRec	receive	receive.component.SteeringWheelLeftRec@15b7986
class receive.component.SteeringWheelLeftRec	doReceive	receive.component.SteeringWheelLeftRec@15b7986
左打方向盘
class order.command.BrakeComm	execute	order.command.BrakeComm@112f614
class receive.component.BrakeRec	receive	receive.component.BrakeRec@1d9dc39
class receive.component.BrakeRec	doReceive	receive.component.BrakeRec@1d9dc39
刹车
class order.command.IgnitionComm	execute	order.command.IgnitionComm@111a3ac
class receive.component.IgnitionRec	receive	receive.component.IgnitionRec@110b053
class receive.component.IgnitionRec	doReceive	receive.component.IgnitionRec@110b053
点火
class order.command.ClutchComm	execute	order.command.ClutchComm@19efb05
class receive.component.ClutchRec	receive	receive.component.ClutchRec@723d7c
class receive.component.ClutchRec	doReceive	receive.component.ClutchRec@723d7c
离合
class order.command.HangOutComm	execute	order.command.HangOutComm@a981ca
class receive.component.HangOutRec	receive	receive.component.HangOutRec@8814e9
class receive.component.HangOutRec	doReceive	receive.component.HangOutRec@8814e9
挂挡
class order.command.OilComm	execute	order.command.OilComm@743399
class receive.component.OilRec	receive	receive.component.OilRec@e7b241
class receive.component.OilRec	doReceive	receive.component.OilRec@e7b241
给油
执行命令----加速
class receive.car.impl.CarAddRec	receive	receive.car.impl.CarAddRec@1d8957f
receive.car.impl.CarAddRec	doReceive	class receive.car.impl.CarAddRec
class order.step.impl.CarAddComm	execute	order.step.impl.CarAddComm@3ee284
class order.command.OilComm	execute	order.command.OilComm@743399
class receive.component.OilRec	receive	receive.component.OilRec@e7b241
class receive.component.OilRec	doReceive	receive.component.OilRec@e7b241
给油
class order.command.ClutchComm	execute	order.command.ClutchComm@19efb05
class receive.component.ClutchRec	receive	receive.component.ClutchRec@723d7c
class receive.component.ClutchRec	doReceive	receive.component.ClutchRec@723d7c
离合
class order.command.HangOutComm	execute	order.command.HangOutComm@a981ca
class receive.component.HangOutRec	receive	receive.component.HangOutRec@8814e9
class receive.component.HangOutRec	doReceive	receive.component.HangOutRec@8814e9
挂挡
class order.command.OilComm	execute	order.command.OilComm@743399
class receive.component.OilRec	receive	receive.component.OilRec@e7b241
class receive.component.OilRec	doReceive	receive.component.OilRec@e7b241
给油

5.2.7 说明

这里命令的集合的实现不能放在享元的工厂中，虽然命令与命令的集合都实现了命令的接口，理论上把命令的集合放在享元的工厂中也不会报错。但是会有执行错误。
原因就是命令的集合在调用命令时的方法：

@Override
	public void execute() {
		System.out.println(this.getClass() + "\texecute\t"
				+ this);
		IntfCommand command = step.poll();
		while(command != null){
			command.execute();
			command = step.poll();
		}
		
	}

可以看到使用的是队列的弹出方法，这个方法具有两个操作：
1.返回队列头部的元素
2.删除当前队列头部的元素，并把头指向下一个元素

也就是说上面的这个方法破坏了数据，无法作为享元工厂的元数据。

那么必须要使用享元提高性能怎么办？
那就在上一层：我们这里的操作是起步，加速这一类的操作，更高一层的操作就是以起步，加速的操作作为原子操作的级别，在这一级别的享元工厂可以把起步、加速作为元数据。

但是命令的发动者的角色可以放在享元的工厂中：
因为发动者的方法没有破坏数据：

@Override
	protected void doReceive() {
		System.out.println(this.getClass().getName() + "\tdoReceive\t"
				+ this.getClass());
		carStart.execute();
	}

只是调用方法。
23种设计模式

    原文作者：算法小白
    原文地址: https://blog.csdn.net/a18792721831/article/details/85170621
    本文转自网络文章，转载此文章仅为分享知识，如有侵权，请联系博主进行删除。
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