java设计模式精讲 Debug 方式+内存分析 第23章 命令模式讲解

23-1 命令模式讲解

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23-2 命令模式coding

我们引入一个业务场景：课程里面是有视频的，我们想要局部关闭某一个视频，或者是局部打开某一个视频，如第一章节是开放的，是可以免费看的，而其他章节的课程就是需要购买了之后才能观看的；现在，管理员决定把第二章节也免费观看，然后又过了一阵，把第三章节的视频给进行开放了；又过一阵，把第二章节给关闭了；就是这么一个业务场景；

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有一个命令类：

public interface Command {
    void execute(); 
}

还有一个视频课程类：

public class CourseVideo {
    private String name;

    public CourseVideo(String name) {
        this.name = name;
    }
    public void open() {
        System.out.println(this.name+"课程开放");
    }
    public void close() {
        System.out.println(this.name+"课程关闭");
    }
}

还有两个课程开启和关闭的类：

public class CloseCourseVideoCommand implements Command {

    private CourseVideo courseVideo;

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

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

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public class OpenCourseVideoCommand implements Command {
    private CourseVideo courseVideo;

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

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

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还有一个添加命令的类：

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();
    }
}

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这个就是现在的类图：

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测试类：

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

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

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测试结果如下：

Java设计模式课程开放
Java设计模式课程关闭

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23-3 命令模式源码-jdk-junit

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