Class LuhnCheckDigit

java.lang.Object

org.apache.commons.validator.routines.checkdigit.ModulusCheckDigit

org.apache.commons.validator.routines.checkdigit.LuhnCheckDigit

All Implemented Interfaces:

Serializable, CheckDigit

public final class LuhnCheckDigit
extends ModulusCheckDigit

Modulus 10 Luhn Check Digit calculation/validation.

Luhn check digits are used, for example, by:

• Credit Card Numbers
• IMEI Numbers - International Mobile Equipment Identity Numbers

Check digit calculation is based on modulus 10 with digits in an odd position (from right to left) being weighted 1 and even position digits being weighted 2 (weighted values greater than 9 have 9 subtracted).

See Wikipedia for more details.

Since:

1.4

See Also:

• Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
static final CheckDigit	LUHN_CHECK_DIGIT	Singleton Luhn Check Digit instance.

Constructor Summary

Constructors

Constructor	Description
LuhnCheckDigit()	Constructs a modulus 10 Luhn Check Digit routine.

Method Summary

Modifier and Type	Method	Description
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, calculateModulus, 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.
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.
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

LUHN_CHECK_DIGIT

public static final CheckDigit LUHN_CHECK_DIGIT

Singleton Luhn Check Digit instance.

Constructor Details

LuhnCheckDigit

public LuhnCheckDigit()

Constructs a modulus 10 Luhn Check Digit routine.

Method Details

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 Luhn (from right to left) odd digits are weighted with a factor of one and even digits with a factor of two. Weighted values > 9, have 9 subtracted

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.