1、what

　　隐藏系统的复杂性，并向客户端提供了一个客户端可以访问系统的接口；

2、解决什么问题？

　　简化客户端的使用，服务端只需要提供一个高级抽象接口；

3、案例

　　去医院看病，可能要去挂号、门诊、划价、取药，让患者或患者家属觉得很复杂，如果有提供接待人员，只让接待人员来处理，就很方便

4、

package com.an.facade;

public interface Drawer {
    void draw();
}


package com.an.facade;

public class CycleDrawer implements Drawer{
    public void draw() {
        System.out.println("cycle draw...");
    }
}


package com.an.facade;

public class SquareDrawer implements Drawer{
    public void draw() {
        System.out.println("square draw...");
    }
}


package com.an.facade;

/**
 * 提供给调用方的高级抽象
 * 封装了具体的实现细节，eg：drawCycle...
 */
public class DrawerFacade {

    private CycleDrawer cycleDrawer;
    private SquareDrawer squareDrawer;

    public DrawerFacade(){
        this.cycleDrawer=new CycleDrawer();
        this.squareDrawer=new SquareDrawer();
    }

    public void drawCycle(){
        cycleDrawer.draw();
    }

    public void drawSquare(){
        squareDrawer.draw();
    }

}


package com.an.facade;

public class Test {

    public static void main(String[] args) {
        DrawerFacade drawerFacade=new DrawerFacade();
        drawerFacade.drawCycle();
        drawerFacade.drawSquare();
    }
}


结果：

cycle draw...
square draw...