ISBN13 check digit: Difference between revisions
→{{header|Java}}
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=={{header|Java}}==
<syntaxhighlight lang="java">
public static void main(String[] args) {
String[] isbn13s = {
"978-0596528126",
"978-0596528120",
"978-1788399081",
"978-1788399083"
};
for (String isbn13 : isbn13s)
System.out.printf("%s %b%n", isbn13, validateISBN13(isbn13));
}
static boolean validateISBN13(String string) {
int[] digits = digits(string.strip().replace("-", ""));
return digits[12] == checksum(digits);
}
static int[] digits(String string) {
int[] digits = new int[13];
int index = 0;
for (char character : string.toCharArray()) {
if (character < '0' || character > '9')
throw new IllegalArgumentException("Invalid ISBN-13");
/* convert ascii to integer */
digits[index++] = Character.digit(character, 10);
}
return digits;
}
static int checksum(int[] digits) {
int total = 0;
int index = 0;
for (int digit : digits) {
if (index == 12) break;
if (index++ % 2 == 1) digit *= 3;
total += digit;
}
return 10 - (total % 10);
}
</syntaxhighlight>
<pre>
978-0596528126 true
978-0596528120 false
978-1788399081 true
978-1788399083 false
</pre>
<br />
An alternate demonstration
<syntaxhighlight lang="java">public static void main(){
System.out.println(isISBN13("978-1734314502"));
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