设计模式的艺术 第二十章中介者模式练习（设计一套图形界面类库，包含若干预定义的窗格（Pane）对象，如 TextPane、ListPane 等，窗格之间不允许直接引用。基于该类库的应用由一个包含一组窗格的窗口（Window）组成，窗口协调窗格之间的行为）

// 中介者类：抽象中介者类public abstract class Mediator {    public abstract void paneChanged(Pane pane);}

// 抽象窗格类：抽象同事类public abstract class Pane {    protected Mediator mediator;
    public void setMediator(Mediator mediator) {        this.mediator = mediator;    }
    public void changed() {        this.mediator.paneChanged(this);    }
    public abstract void update();}

// 窗口中介者类：具体中介者类public class WindowMediator extends Mediator{    public TextPane textPane;    public ListPane listPane;    public GraphicPane graphicPane;
    @Override    public void paneChanged(Pane pane) {        if (pane == this.textPane) {            listPane.select();            graphicPane.draw();        }        if (pane == this.listPane) {            textPane.update();            graphicPane.update();        }        if (pane == this.graphicPane) {            textPane.update();            listPane.update();        }    }}

// 文本窗格类：具体同事类public class TextPane extends Pane{    @Override    public void update() {        System.out.println("textPane对象新增内容");    }}

// 列表窗格类：具体同事类public class ListPane extends Pane{    @Override    public void update() {        System.out.println("listPane对象新增内容");    }
    public void select() {        System.out.println("listPane对象选中内容");    }}

// 图形窗格类：具体同事类public class GraphicPane extends Pane{    @Override    public void update() {        System.out.println("graphicPane对象新增内容");    }
    public void draw() {        System.out.println("graphicPane对象绘制内容");    }}

public class Client {    public static void main(String[] args) {        WindowMediator windowMediator;        windowMediator = new WindowMediator();
        TextPane textPane = new TextPane();        ListPane listPane = new ListPane();        GraphicPane graphicPane = new GraphicPane();
        textPane.setMediator(windowMediator);        listPane.setMediator(windowMediator);        graphicPane.setMediator(windowMediator);
        windowMediator.textPane = textPane;        windowMediator.listPane = listPane;        windowMediator.graphicPane = graphicPane;
        textPane.changed();        System.out.println();        graphicPane.changed();    }}

listPane对象选中内容graphicPane对象绘制内容
textPane对象新增内容listPane对象新增内容