Java Wildcard String Matching

Posted 2008-12-15 in Java by Johann.

This entry contains code examples of Java pattern matching with wildcards.

Note that wildcard matching is not the same as the .* regular expression which matches any number of characters – a wildcard matches only one character. Wildcards are usually encoded as ., but the actual value may vary across libraries.

StringSearch

StringSearch 1.2 comes with two wildcard pattern matching algorithms, BNDMWildcards and ShiftOrWildcards. Generally, BNDMWildcards will be faster, which is why I removed ShiftOrWildcards in version 2.

public void testStringSearch() {
    BNDMWildcards bndm = new BNDMWildcards();
    Object compiled = bndm.processString("bla.blorb");
    // "bla?blorb" for StringSearch 1.2
    assertEquals(3,
        bndm.searchString("la bla0blorb null", "bla.blorb", compiled));
}

java.util.regex.Pattern

The java.util.regex.Pattern API isn’t very compact, but of course it does offer more than just wildcards.

public void testJavaUtilRegex() {
    Pattern searchPattern = Pattern.compile("bla.blorb");
    Matcher m = searchPattern.matcher("la bla0blorb null");
    assertTrue(m.find());
    assertEquals(3, m.start());
}

Jakarta Oro

ORO offers many PatternMatcher implementations. In this example, I am using the Perl5Matcher class.

public void testJakartaORO() throws MalformedPatternException {
    Pattern p = new Perl5Compiler().compile("bla.blorb");
    Perl5Matcher matcher = new Perl5Matcher();
    assertTrue(matcher.contains("la bla0blorb null", p));
    MatchResult result = matcher.getMatch();
    assertEquals(3, result.beginOffset(0));
}

Case Insensitive Search

All of the APIs presented here support case-insensitive string matching. The case insensitive option is simply compiled into the pattern in the compile phase.

StringSearch

This example requires StringSearch version 2 or greater.

    BNDMWildcardsCI bndm = new BNDMWildcardsCI();
    Object compiled = bndm.processString("bla.blorb");
…

java.util.regex.Pattern

    Pattern searchPattern = Pattern.compile("bla.blorb",
        Pattern.CASE_INSENSITIVE);
…

Jakarta ORO

        Pattern p = new Perl5Compiler().compile("bla.blorb",
                Perl5Compiler.CASE_INSENSITIVE_MASK);
…