Sha256: 24882b83e5d54c3e2a18fafc2e308d2e1016c026a8d16dee7892788a7a14c5d0
Contents?: true
Size: 1.57 KB
Versions: 300
Compression:
Stored size: 1.57 KB
Contents
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Pattern;
final class LuhnValidator {
private static final Pattern SPACE_PATTERN = Pattern.compile("\\s+");
boolean isValid(final String candidate) {
final String sanitizedCandidate = SPACE_PATTERN.matcher(candidate).replaceAll("");
if (sanitizedCandidate.length() <= 1) {
return false;
}
// We need to alter every second digit counting from the right. Reversing makes this easy!
final String reversedSanitizedCandidate = reverse(sanitizedCandidate);
final List<Integer> computedDigits = new ArrayList<>();
for (int charIndex = 0; charIndex < reversedSanitizedCandidate.length(); charIndex++) {
int inputDigit = Character.digit(reversedSanitizedCandidate.charAt(charIndex), 10);
/*
* Character.digit returns a negative int if the supplied character does not represent a digit with respect
* to the given radix.
*/
if (inputDigit < 0) {
return false;
}
if (charIndex % 2 == 1) {
inputDigit = 2 * inputDigit;
if (inputDigit > 9) {
inputDigit -= 9;
}
}
computedDigits.add(inputDigit);
}
final int digitSum = computedDigits.stream().mapToInt(Integer::intValue).sum();
return digitSum % 10 == 0;
}
private String reverse(final String string) {
return new StringBuilder(string).reverse().toString();
}
}
Version data entries
300 entries across 300 versions & 1 rubygems