# Class ECNumberCheckDigit

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

All Implemented Interfaces:
  `Serializable, CheckDigit`

public final class ECNumberCheckDigit extends ModulusCheckDigit
Modulus 11 EC number Check Digit calculation/validation.

The European Community number (EC number) is a unique seven-digit identifier that is assigned to chemical substances. For example, the EC number of arsenic is 231-148-6:

Check digit calculation is based on modulus 11 with digits being weighted based on their position (from left to right).

For further information see Wikipedia - EC number.

Since:
  1.9.0
See Also:
  - Serialized Form

- ## Method Summary

  Modifier and Type
  Method
  Description
  `String`
  `calculate(String code)`
  Calculates a modulus Check Digit for a code which does not yet have one.
  `static CheckDigit`
  `getInstance()`
  Gets the singleton instance of this validator.
  `boolean`
  `isValid(String code)`
  Validates a modulus check digit for a 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

  `calculateModulus, getModulus, sumDigits, toCheckDigit, toInt`
  Modifier and Type
  Method
  Description
  `protected int`
  `calculateModulus(String code, boolean includesCheckDigit)`
  Calculates the modulus for a code.
  `int`
  `getModulus()`
  Gets the modulus value this check digit routine is based on.
  `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`

- ## Method Details

  - ### getInstance

    public static CheckDigit getInstance()
    Gets the singleton instance of this validator.
    Returns:
      A singleton instance of the EC Number validator.

  - ### calculate

    public String calculate(String code) throws CheckDigitException
    Calculates a modulus Check Digit for a code which does not yet have one.
    Specified by:
      `calculate` in interface `CheckDigit`
    Overrides:
      `calculate` in class `ModulusCheckDigit`
    Parameters:
      `code` - The code for which to calculate the Check Digit; the check digit should not be included.
    Returns:
      The calculated Check Digit.
    Throws:
      `CheckDigitException` - if an error occurs calculating the check digit.

  - ### isValid

    public boolean isValid(String code)
    Validates a modulus check digit for a code.
    Specified by:
      `isValid` in interface `CheckDigit`
    Overrides:
      `isValid` in class `ModulusCheckDigit`
    Parameters:
      `code` - The code to validate.
    Returns:
      `true` if the check digit is valid, otherwise `false`.

  - ### 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 EC number digits are weighted by their position from left to right.

    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.