外观模式

我们通过外观的包装，使应用程序只能看到外观对象，而不会看到具体的细节对象，这样无疑会降低应用程序的复杂度，并且提高了程序的可维护性。
Facade.java

public class Facade {
    private SubSystemOne subSystemOne;
    private SubSystemTwo subSystemTwo;
    private SubSystemThree subSystemThree;

    public Facade(){
        this.subSystemOne=new SubSystemOne();
        this.subSystemTwo=new SubSystemTwo();
        this.subSystemThree=new SubSystemThree();
    }
    public void MethodA(){
        subSystemOne.MethodOne();
        subSystemThree.MethodThree();
    }
    public void MethodB(){
        subSystemTwo.MethodTwo();
        subSystemThree.MethodThree();
    }
}

SubSystemOne.java

public class SubSystemOne {
    public void MethodOne(){
        System.out.println("子系统方法一");
    }
}

SubSystemTwo

public class SubSystemTwo {
    public void MethodTwo(){
        System.out.println("子系统方法二");
    }
}

SubSystemThree

public class SubSystemThree {
    public void MethodThree(){
        System.out.println("子系统方法二");
    }
}

Client.java

public class Client {
    public static void main(String args[]){
      Facade facade=new Facade();
      facade.MethodA();
      facade.MethodB();
    }
}