CUSIP Source Code

The algorithm used to assign [CUSIP]s a variation of the LUHN algorithm. CUSIPs are very important for being able to uniquely identify securities. For example, I've used the code below to validate when a user has entered a valid CUSIP number.

Source Code

<geshi lang="java5"> /**

* This class impliments the 
* Modulus 10 Double Add Double in order
* to check if a <a href="http://en.wikipedia.org/wiki/CUSIP">CUSIP</A>
* is valid.
* @author Brian Egge
*/

public class CusipValidator {

 public static boolean isValid(String ccNum) {

   char number[] = ccNum.toCharArray();

   int len = number.length;
   int sum = 0;
   for (int i = 0; i < len - 1; i++) {
     int num = mapChar(number[i]);

     // Double all the odd digits
     if (i % 2 != 0)
       num *= 2;

     // Combine digits.  i.e., 16 = (1 + 6) = 7
     if (num > 9)
       num = (num % 10) + (num / 10);
     sum += num;
   }

   int checkDigit = mapChar(number[number.length - 1]);
   
   // This is the mathmatical modulus - not the remainder.  i.e., 10 mod 7 = 3
   int mod = (10 - (sum % 10)) % 10;
   if (mod == checkDigit) {
     return true;
   }

   return false;
 }

 /**
  * Standard & Poor's maps A..Z to 10..35 
  * @param c
  * @return numeric value of the letter
  */
 private static int mapChar(char c) {
   if (c >= '0' && c <= '9')
     return c - '0';
   return c - 'A' + 10;
 }

} </geshi>

Test case

<geshi lang="java5"> public class CusipValidatorTest extends TestCase {

 public void testCUSIP() {
   assertTrue(CusipValidator.isValid("31430F200"));
   assertTrue(CusipValidator.isValid("037833100")); // Apple
   assertTrue(CusipValidator.isValid("316549401"));
   assertTrue(CusipValidator.isValid("022615AC2"));
   assertTrue(CusipValidator.isValid("931142103")); // Walmart
   assertTrue(CusipValidator.isValid("883199AQ4"));
   assertTrue(CusipValidator.isValid("14911QGW5"));
   assertTrue(CusipValidator.isValid("14911QHM6"));
   assertTrue(CusipValidator.isValid("339072407"));
   assertTrue(CusipValidator.isValid("3133XBC78"));
   assertTrue(CusipValidator.isValid("808905AB9"));
   
   assertFalse(CusipValidator.isValid("2005"));
   assertFalse(CusipValidator.isValid("?"));
 }

} </geshi>