Cannot find any information on property 'X' in a bean of type 'Y'

javabean:

package bepa1;

public class TiXing
{
   double sd=1;
   double xd=3;
   double gao=2;
   double TiXingarea=0;
  

   public TiXing()
   {
      sd=1;
   }

   public double getsd()
   {
      return sd;
   }

   public void setsd(double newSd)
   {
      sd=newSd;
   }
   public double getxd()
   {
      return xd;
   }

   public void setxd(double newXd)
   {
      xd=newXd;
   }

   public double getGao()
   {
      return gao;
   }

   public void setGao(double newGao)
   {
      gao=newGao;
   }

   public double getTiXingarea()
   {
      TiXingarea=(sd+xd)*gao/2;
      return TiXingarea;
   }

 
}