C#

public class Foo : System.Attribute
{
  public int [] bar;
  public Foo(params int [] a)
  {
    bar = a;
  }
}

public class Foo
{
  public int bar;
  public Foo(int a)
  {
    bar = a;
  }
}

public class What
{
}

class Foo
{
  public Foo(string blah){...}
}

abstract class Poo : Foo
{
  //why should here be a constructor? 
}

abstract class CreditCard
{
    //private CreditCard(){}


    //*************************************************
    //  Input:    string representing a credit card
    //        number.
    //
    //  Returns:  true if a valid credit card number
    //            false if not
    //*************************************************
    public static bool Validate(string CreditCardNumber)
    {
        int sum = 0;

        for(int i = 0; i < CreditCardNumber.Length; i++)
        {   // odd number here
            if((int)CreditCardNumber[i]%2 != 0)
            {
                if((int)CreditCardNumber[i] * 2 > 9)
                    sum += ((int)CreditCardNumber[i] * 2) - 9;
                else
                    sum += (int)CreditCardNumber[i] * 2;
            }
            else    // even number here
            {
                if((int)CreditCardNumber[i] != 0)
                    sum += (int)CreditCardNumber[i];
            }
        }

        return(Convert.ToBoolean(sum%10));
    }

}

abstract class Poo
{
  ...
}
public class Foo : Poo
{
  Foo(){}
  ...
}

Foo f = new Foo();