命令模式

1.定义：将“请求”封装成对象，以便使用不同的请求；
　　　   命令模式解决了应用程序中对象的职责以及它们之间的通信方式。

2.类型：行为型

3.适用场景：请求调用者和请求接收者需要解耦，使得调用者和接收者不直接交互；
　　　　　   需要抽象出等待执行的行为。

4.优点：降低耦合，容易扩展新命令或者一组命令。

5.缺点：命令的无限扩展会增加类的数量，提高系统实现复杂度。

6.相关设计模式：备忘录模式

7.实例目录package

8.实例UML类图

9.代码

package com.geely.design.pattern.behavioral.command;

public class CourseVideo {
    private String name;

    public CourseVideo(String name) {
        this.name = name;
    }
    public void open(){
        System.out.println(this.name + "课程视频开发");
    }
    public void close(){
        System.out.println(this.name + "课程视频关闭");
    }
}

package com.geely.design.pattern.behavioral.command;

public interface Command {
    void execute();
}

package com.geely.design.pattern.behavioral.command;

public class CloseCourseVideoCommand implements Command {
    private CourseVideo courseVideo;

    public CloseCourseVideoCommand(CourseVideo courseVideo) {
        this.courseVideo = courseVideo;
    }

    @Override
    public void execute() {
        courseVideo.close();
    }
}

package com.geely.design.pattern.behavioral.command;

public class OpenCourseVideoCommand implements Command {
    private CourseVideo courseVideo;

    public OpenCourseVideoCommand(CourseVideo courseVideo){
        this.courseVideo = courseVideo;
    }

    @Override
    public void execute() {
        courseVideo.open();
    }
}

package com.geely.design.pattern.behavioral.command;

import java.util.ArrayList;
import java.util.List;

public class Staff {
    private List<Command> commandList = new ArrayList<>();

    public void addCommand(Command command){
        commandList.add(command);
    }

    public void executeCommands(){
        for(Command command : commandList){
            command.execute();
        }
        commandList.clear();
    }
}

package com.geely.design.pattern.behavioral.command;

public class Test {
    public static void main(String[] args) {
        CourseVideo courseVideo = new CourseVideo("Java设计模式精讲 -- By Geely");
        OpenCourseVideoCommand openCourseVideoCommand = new OpenCourseVideoCommand(courseVideo);
        CloseCourseVideoCommand closeCourseVideoCommand = new CloseCourseVideoCommand(courseVideo);

        Staff staff = new Staff();
        staff.addCommand(openCourseVideoCommand);
        staff.addCommand(closeCourseVideoCommand);

        staff.executeCommands();
    }
}