ISBN validation In Java

Use Jakarta-ORO for ISBN validation.

The Jakarta-ORO Java classes are a set of text-processing
 Java classes that provide Perl5 compatible regular
 expressions, AWK-like regular expressions, 
glob expressions, and utility classes 
for performing substitutions, 
splits, filtering filenames, etc.

Download Jakarta-ORO jar

import org.apache.oro.text.perl.Perl5Util;

public class ISBNValidator {

  private static final String SEP = "(\\-|\\s)";
  private static final String GROUP = "(\\d{1,5})";
  private static final String PUBLISHER = "(\\d{1,7})";
  private static final String TITLE = "(\\d{1,6})";
  private static final String CHECK_ISBN10 = "([0-9X])";
  private static final String CHECK_ISBN13 = "(\\d)";
  private static final String PREFIX = "(978|979)";

  private static final String ISBN10_PATTERN = "/^" + GROUP
                     + SEP + PUBLISHER + SEP + TITLE + SEP
                     + CHECK_ISBN10 + "$/";

  private static final String ISBN13_PATTERN = "/^" + 
           PREFIX + SEP + GROUP + SEP + PUBLISHER + SEP
           + TITLE + SEP + CHECK_ISBN13 + "$/";

  private static final String 
                       EAN13_PATTERN = "/^" + PREFIX + "\\d{10}$/";

  public ISBNValidator() {
    super();
  }

  public boolean isValid(String isbn) {
    return isValidISBN10(isbn) || isValidISBN13(isbn);
  }

  public boolean isValidISBN10(String isbn) {
    if (isbn == null || isbn.length() < 10 || isbn.length() > 13) {
      return false;
    }

    if (isFormatted(isbn) && !isValidPatternISBN10(isbn)) {
      return false;
    }

    isbn = cleanISBN10(isbn);
    if (isbn.length() != 10) {
      return false;
    }

    return (sumISBN10(isbn) % 11) == 0;
  }

  public boolean isValidISBN13(String isbn) {
    if (isbn == null || isbn.length() < 13 || isbn.length() > 17) {
      return false;
    }

    if (isFormatted(isbn)) {
      if (!isValidPatternISBN13(isbn)) {
        return false;
      }
      isbn = toEAN13(isbn);
    }
    return isValidEAN13(isbn);
  }

  public boolean isValidEAN13(String ean13) {
    if (ean13 == null || ean13.length() != 13 || !isValidPatternEAN13(ean13)) {
      return false;
    }

    return (sumEAN13(ean13) % 10) == 0;
  }

  private int sumISBN10(String isbn) {
    int total = 0;
    for (int i = 0; i < 9; i++) {
      int weight = 10 - i;
      total += (weight * toInt(isbn.charAt(i)));
    }
    total += toInt(isbn.charAt(9)); // add check digit
    return total;
  }

  private int sumEAN13(String isbn) {
    int total = isbn.charAt(0);
    for (int i = 1; i < 13;) {
      total += (3 * isbn.charAt(i++)) + isbn.charAt(i++);
    }

    return total;
  }

  private String cleanISBN10(String isbn) {
    StringBuffer buf = new StringBuffer(10);

    for (int i = 0; i < isbn.length(); i++) {
      char digit = isbn.charAt(i);
      if (Character.isDigit(digit) || (digit == 'X')) {
        buf.append(digit);
      }
    }

    return buf.toString();
  }

  private String toEAN13(String isbn) {
    StringBuffer buf = new StringBuffer(13);

    for (int i = 0; i < isbn.length(); i++) {
      char digit = isbn.charAt(i);
      if (Character.isDigit(digit)) {
        buf.append(digit);
      }
    }

    return buf.toString();
  }

  private int toInt(char ch) {
    return (ch == 'X') ? 10 : Character.getNumericValue(ch);
  }

  private boolean isFormatted(String isbn) {
    return ((isbn.indexOf('-') != -1) || (isbn.indexOf(' ') != -1));
  }


  private boolean isValidPatternISBN10(String isbn) {
    return new Perl5Util().match(ISBN10_PATTERN, isbn);
  }

  private boolean isValidPatternISBN13(String isbn) {
    return new Perl5Util().match(ISBN13_PATTERN, isbn);
  }


  private boolean isValidPatternEAN13(String isbn) {
    return new Perl5Util().match(EAN13_PATTERN, isbn);
  }

}