我是初学者 下面的错误怎么该啊！！！！
public class Apply
{
    public static void main (String[]args)
            {static int x;
                    int y;
                    x=10;
                    Apply.pt=new Apply;
                    pt.y=20;
              System.out.println("x");
              System.out.println("y");
            }
   
class Best extends Apply
{
         public static void main(String[]args)
         { static int z;
         z=30;
         System.out.println("x");
         System.out.println("y");
         System.out.println("z");
         }
}
}