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();  } }