# Class ABANumberCheckDigit

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

All Implemented Interfaces:
  `Serializable, CheckDigit`

public final class ABANumberCheckDigit extends ModulusCheckDigit
Modulus 10 ABA Number (or Routing Transit Number (RTN)) Check Digit calculation/validation.

ABA Numbers (or Routing Transit Numbers) are a nine digit numeric code used to identify American financial institutions for things such as checks or deposits (ABA stands for the American Bankers Association).

Check digit calculation is based on modulus 10 with digits being weighted based on their position (from right to left) as follows:

- Digits 1, 4 and & 7 are weighted 1
- Digits 2, 5 and & 8 are weighted 7
- Digits 3, 6 and & 9 are weighted 3

For further information see Wikipedia - Routing transit number.

Since:
  1.4
See Also:
  - Serialized Form

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `static final CheckDigit`
  `ABAN_CHECK_DIGIT`
  Singleton Routing Transit Number Check Digit instance.

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `ABANumberCheckDigit()`
  Constructs a modulus 10 Check Digit routine for ABA Numbers.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `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

  `calculate, calculateModulus, getModulus, 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.
  `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

  - ### ABAN_CHECK_DIGIT

    public static final CheckDigit ABAN_CHECK_DIGIT
    Singleton Routing Transit Number Check Digit instance.

- ## Constructor Details

  - ### ABANumberCheckDigit

    public ABANumberCheckDigit()
    Constructs a modulus 10 Check Digit routine for ABA Numbers.

- ## Method Details

  - ### isValid

    public boolean isValid(String code)
    Validates a modulus check digit for a code.

    The weight is taken from `rightPos`, which does not change when a character is prepended, so `ModulusCheckDigit` would accept an over-length code whose leading digit lands on a no-op weight (for example `0123456780`). The nine-character length is checked here before the check digit test.

    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.

    ABA Routing numbers are weighted in the following manner:

            left position: 1  2  3  4  5  6  7  8  9
                   weight: 3  7  1  3  7  1  3  7  1

    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.