com.thelastcheck.commons.base.utils.CheckDigitLuhnMod10Verifier Maven / Gradle / Ivy
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* Copyright (c) 2009-2015 The Last Check, LLC, All Rights Reserved
*
* Licensed under the Apache License, Version 2.0 (the "License");
* You may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
******************************************************************************/
package com.thelastcheck.commons.base.utils;
public class CheckDigitLuhnMod10Verifier implements CheckDigitVerifier {
private static CheckDigitVerifier instance = new CheckDigitLuhnMod10Verifier();
public static CheckDigitVerifier getInstance() {
return instance;
}
private CheckDigitLuhnMod10Verifier() {
}
public boolean isValid(String id) {
int currentDigit;
int idSum = 0;
int position = 0; //the current position number (to calc odd/even proc)
for (int i = id.length() - 1; i >= 0; i--) {
//get the current rightmost digit from the string
String idCurrentRightmostDigit = id.substring(i, i + 1);
//parse to int the current rightmost digit, if fail return false (not-valid id)
try {
currentDigit = Integer.parseInt(idCurrentRightmostDigit);
} catch (NumberFormatException e) {
return false;
}
// double value of every 2nd rightmost digit
// if value 2 digits (for example: 18 ),
// then sum the digits (made easy by subtracting 9, for example, 18 -> 1+8 = 9, same as 18-9 = 9)
if (position % 2 != 0) {
currentDigit *= 2;
if (currentDigit > 9)
currentDigit -= 9;
}
position++; //increase the proc number
//summarize the processed digits
idSum += currentDigit;
}
//if digits sum is exactly divisible by 10, return true (valid), else false (not-valid)
return (idSum % 10 == 0);
}
}