# Class ISINCheckDigit

java.lang.Object
org.apache.commons.validator.routines.checkdigit.ModulusCheckDigit
org.apache.commons.validator.routines.checkdigit.ISINCheckDigit

All Implemented Interfaces:
  `Serializable, CheckDigit`

public final class ISINCheckDigit extends ModulusCheckDigit
Modulus 10 ISIN (International Securities Identifying Number) Check Digit calculation/validation.

ISIN Numbers are 12 character alphanumeric codes used to identify Securities.

Check digit calculation uses the Modulus 10 Double Add Double technique with every second digit being weighted by 2. Alphabetic characters are converted to numbers by their position in the alphabet starting with A being 10. Weighted numbers greater than ten are treated as two separate numbers.

See Wikipedia - ISIN for more details.

Since:
  1.4
See Also:
  - Serialized Form

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `static final CheckDigit`
  `ISIN_CHECK_DIGIT`
  Singleton ISIN Check Digit instance.

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `ISINCheckDigit()`
  Constructs an ISIN Identifier Check Digit routine.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `protected int`
  `calculateModulus(String code, boolean includesCheckDigit)`
  Calculate the modulus for an ISIN code.
  `protected int`
  `weightedValue(int charValue, int leftPos, int rightPos)`
  Calculates the weighted value of a character in the code at a specified position.

  ### Methods inherited from class ModulusCheckDigit

  `calculate, getModulus, isValid, sumDigits, toCheckDigit, toInt`
  Modifier and Type
  Method
  Description
  `String`
  `calculate(String code)`
  Calculates a modulus Check Digit for a code which does not yet have one.
  `int`
  `getModulus()`
  Gets the modulus value this check digit routine is based on.
  `boolean`
  `isValid(String code)`
  Validates a modulus check digit for a code.
  `static int`
  `sumDigits(int number)`
  Adds together the individual digits in a number.
  `protected String`
  `toCheckDigit(int charValue)`
  Converts an integer value to a check digit.
  `protected int`
  `toInt(char character, int leftPos, int rightPos)`
  Converts a character at a specified position to an integer value.

  ### Methods inherited from class Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Field Details

  - ### ISIN_CHECK_DIGIT

    public static final CheckDigit ISIN_CHECK_DIGIT
    Singleton ISIN Check Digit instance.

- ## Constructor Details

  - ### ISINCheckDigit

    public ISINCheckDigit()
    Constructs an ISIN Identifier Check Digit routine.

- ## Method Details

  - ### calculateModulus

    protected int calculateModulus(String code, boolean includesCheckDigit) throws CheckDigitException
    Calculate the modulus for an ISIN code.
    Overrides:
      `calculateModulus` in class `ModulusCheckDigit`
    Parameters:
      `code` - The code to calculate the modulus for.
      `includesCheckDigit` - Whether the code includes the Check Digit or not.
    Returns:
      The modulus value.
    Throws:
      `CheckDigitException` - if an error occurs calculating the modulus for the specified code.

  - ### weightedValue

    protected int weightedValue(int charValue, int leftPos, int rightPos)
    Calculates the weighted value of a character in the code at a specified position.

    For ISIN (from right to left) odd digits are weighted with a factor of one and even digits with a factor of two. Weighted values are reduced to their digital root

    Specified by:
      `weightedValue` in class `ModulusCheckDigit`
    Parameters:
      `charValue` - The numeric value of the character.
      `leftPos` - The position of the character in the code, counting from left to right.
      `rightPos` - The position of the character in the code, counting from right to left.
    Returns:
      The weighted value of the character.