关于抽象工厂和具体工厂的问题
下面是有关抽象工厂和具体工厂的三个裁剪后的类，请前辈们先看下：
public abstract class BasetableFactory{
  private static final String classname="com.bwm.database.DbBasetableFactory";
  private static BasetableFactory factory;
  public static BasetableFacotry getInstance(){
  Class c=Class.forName(classname);
  factory=(BasetableFactory)c.newInstance();
  return new BasetableFactoryProxy(factory);
}
  public abstract int getRow(String sql);
}
public class BasetableFactoryProxy extends BasetableFactory{
  private BasetableFactory factory;
  public BasetableFactoryProxy(BasetableFactory factory){
  this.factory=factory;
}
  public int getRow(String sql){
  return factory.getRow(sql);
}
}
public class DbBasetableFactory extends BasetableFactory{
  public DbBasetableFactory(){}
  public int getRow(String sql){
  return DataBase.getRow(sql);
}
}
  我想问的是：案例里这样做好象拐来拐去的封装了好多层，直接使用
  抽象工厂BasetableFactory和具体工厂DbBasetableFactory也可以
  实现所要的功能，为什么还要再构造多一个类BasetableFactoryProxy来
  实例化BasetableFactoryProxy，这样做有什么好处？
  谢谢！

------解决方案--------------------
去看看接口和抽象类的作用