Miscellany

public class ISBN
{
	private String isbn;
	
	public ISBN(String input)
	{
		isbn = input;
	}
	
	public boolean isValidISBN()
 {
  if (isbn.length() != 10)
   return false;
   
  int total = 0;
  int ctr = 10;
  int a;
  for(a = 0; a < isbn.length()-1; a++)
  {
   if (!Character.isDigit(isbn.charAt(a)))
    return false;
   total += ctr * Integer.parseInt(isbn.substring(a,a+1));
   System.out.println(total);
   ctr--;
  }
  if (isbn.charAt(isbn.length()-1) == 'x')
   if ((total+10) % 11 == 0)
    return true;
    
  int d10 = total % 11;
  System.out.println("\n" + d10);
  if (Character.digit(isbn.charAt(isbn.length()-1),10) == d10)
   return true;
  System.out.println(total / d10);
  return false;
}
}




import javax.swing.JOptionPane; 
  
public class ISBNDriver
{
 public static void main (String [] args)
 {
  String input = JOptionPane.showInputDialog("Enter an ISBN");
  ISBN test = new ISBN(input);
  
  if (test.isValidISBN())
   System.out.println("Is a valid ISBN");
  else
   System.out.println("Is a valid ISBN.");
 }
}