here's the code:

class Acount
{ int sum ; String owner ; //these seem to make sense 
    //a constructor or two 
    public Acount () 
    { this.sum = 0 ; this.owner = "John Doe" ; }

    public Acount (String name) 
    {this.sum = 0 ; this.owner = name ; } 

    public Acount (String name, int sum) 
    {this.sum = sum ; this.owner = name ; } 

    //prints an acount in the format "owner" "sum" 
    public static void printAcount (Acount Acount) 
    {System.out.print (Acount.owner) ; System.out.print (" ") ; System.out.println (Acount.sum) ; } 

    public static void main (String[]arg) 
    { 
        Acount Acount1 = new Acount ("david", 100) ; 
        System.out.println ("heres the first acount as it was created:") ; 
        printAcount (Acount1) ; 
        System.out.println ("now i changed one of its instance varaibles with a static method") ; 
        upOne (Acount1) ; 
        printAcount (Acount1) ; 
    } 

    public static Acount upOne (Acount Acount)
    { 
        Acount.sum = Acount.sum + 1 ; 
        return Acount ; 
    } 
}

here's the error:

Exception in thread "main" java.lang.NoClassDefFoundError: Acount/java

What went wrong?