java接口中的代理设计模式代码时实践

package www.miao.java;
interface ISubject{
  //核心功能是买电脑
  public void buyComputer();
}
//真实业务实现
class RealSubject implements ISubject{

  public void buyComputer() {
    System.out.println("买一台外星人电脑");
  }
}
class proxySubject implements ISubject{
  //真实的操作业务
  private ISubject subject;

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


  public void produceComputer() {
    System.out.println("生产外星人电脑");
  }

  public void afterSale()
  {
    System.out.println("外星人电脑售后");
  }


  public void buyComputer() {
    //真实操作前的准备
    this.produceComputer();
    //调用真实业务
    this.subject.buyComputer();
    //操作后的收尾
    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();
  }
 }