Paysafe Check Digit calculation/validation based on Apache Commons validator

PaysafeCheckDigit.java

import org.apache.commons.validator.routines.checkdigit.CheckDigit;
import org.apache.commons.validator.routines.checkdigit.CheckDigitException;
import org.apache.commons.validator.routines.checkdigit.ModulusCheckDigit;

/**
 * Modulus 10 <b>Paysafe</b> Check Digit calculation/validation.
 * <p>
 * Check digit calculation is based on <i>modulus 10</i> with digits in
 * an <i>odd</i> position (from left to right) being weighted 1 and <i>even</i>
 * position digits being weighted 3.
 * <p>
 *
 * Created by Nikos Linakis on 11/12/2017.
 */

public class PaysafeCheckDigit extends ModulusCheckDigit {

    /** Singleton Paysafe Check Digit instance */
    public static final CheckDigit PAYSAFE_CHECK_DIGIT = new PaysafeCheckDigit();

    /** weighting given to digits depending on their left position */
    private static final int[] POSITION_WEIGHT = new int[] {3, 1};


    /**
     * Construct a modulus 10 Check Digit routine
     */
    public PaysafeCheckDigit() {
        super(10);  // CHECKSTYLE IGNORE MagicNumber
    }

    /**
     * <p>Calculates the <i>weighted</i> value of a character in the
     * code at a specified position.</p>
     *
     * <p>For Paysafe (from left to right) <b>odd</b> digits are weighted
     * with a factor of <b>one</b> and <b>even</b> digits with a factor
     * of <b>three</b>.</p>
     *
     * @param charValue The numeric value of the character.
     * @param leftPos The position of the character in the code, counting from left to right
     * @param rightPos The position of the character in the code, counting from right to left
     * @return The weighted value of the character.
     */
    @Override
    protected int weightedValue(int charValue, int leftPos, int rightPos) {
        int weight = POSITION_WEIGHT[leftPos % 2];
        return charValue * weight;
    }

    @Override
    public boolean isValid(String code) {
        if (code == null || code.length() == 0) {
            return false;
        }
        try {
            // last character digit is our check digit
            int checkDigit = Integer.parseInt(code.substring(code.length() - 1));

            // calculate the mod result of the code sans the check digit using the weightedValue logic
            int modulusResult = calculateModulus(code.substring(0, code.length() - 1), false);

            // the difference of the modulus result from 10 is the check digit.
            // In case the modulus result is 0 then our remainder is 0.
            // Because 0 IS a multiple of 10 (10 * 0 = 0).
            int remainder = modulusResult == 0 ? 0 : 10 - modulusResult;

            return (remainder == checkDigit);
        } catch (CheckDigitException ex) {
            return false;
        }
    }
}

Usage:

PaysafeCheckDigit.PAYSAFE_CHECK_DIGIT.isValid("0000000000000000")

Add Apache Commons validator for Android

dependencies {
    compile 'commons-validator:commons-validator:1.6'
}