It can be used to evaluate RegExp expression in your application. It can be injected into or created by hand. Some simple example shows that below:

@Inject
public void setMatcher(PatternMatcher matcher) {
    this.matcher = matcher;
}

private boolean matchesWildcard(String pattern, String data) {
    Object exp = matcher.compilePattern(pattern);
    return matcher.match(new HashMap<String, String>(), data, exp);
}