概念：兩個子類共同實現一個介面，其中一個子類負責真實業務實現，另一個子類完成輔助真實業務主題的操作。

package  www.miao.java;
interface  ISubject{
    //核心功能是買電腦
    public void buyComputer();
}
//真實業務實現
class RealSubject implements ISubject{

    public void buyComputer() {
        System.out.println("買一臺外星人電腦");
    }
}
class proxySubject implements
 
 ISubject{
    //真實的操作業務
    private ISubject subject;

    public proxySubject(ISubject subject) {
        this.subject = subject;
    }


    public void produceComputer() {
        System.out.println("生產外星人電腦");
    }

    public void afterSale()
    {
        System.out.println("外星人電腦售後");
    }


    public
 
 void buyComputer() {
        //真實操作前的準備
        this.produceComputer();
        //呼叫真實業務
        this.subject.buyComputer();
        //操作後的收尾
        this.afterSale();
    }
}

class Factory{
    public static  ISubject getInstance()
    {
        return new proxySubject(new RealSubject());
    }
}
public
 
 class Test{
    public static void main(String [] args){
        ISubject subject = Factory.getInstance();
        subject.buyComputer();
    }
 }