我是初学者 下面的错误怎么该啊！！！！

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");
         }
}
}
----------------解决方案--------------------------------------------------------
public class Apply
{
    static int x = 10;
    int y;
    public static void main (String[] args)
       {
              Apply  pt=new Apply();
           pt.y=20;
           System.out.println(x);
           System.out.println(pt.y);
        }
           
           
    }





class Best extends Apply
{
     static int z =30;
     
     public static void main(String[] args)
        {
         System.out.println(x);
         //System.out.println("y");  (不要）
         System.out.println(z);
         }
}
----------------解决方案--------------------------------------------------------