How do you like my JQuery implementation in Java?

Example usage.java

String result = $(document).find("#result").text();

JQuery.java

package no.java.incogito.tcs;

import fj.F;
import fj.pre.Show;
import fj.data.List;
import fj.data.Option;
import static fj.data.Option.some;
import fj.data.Tree;
import no.java.incogito.tcs.XmlTree.XmlElement;
import no.java.incogito.tcs.XmlTree.XmlNode;
import org.w3c.dom.Document;

/**
* @author <a href="mailto:trygvis@java.no">Trygve Laugst&oslash;l</a>
* @version $Id$
*/
public class JQuery {

    private final XmlTree document;
    private final List<Tree<XmlNode>> matches;

    public JQuery(XmlTree document, List<Tree<XmlNode>> matches) {
        this.document = document;
        this.matches = matches;
    }

    public JQuery(XmlTree document, Option<Tree<XmlNode>> match) {
        this.document = document;
        this.matches = match.toList();
    }

    public JQuery find(String selector) {
        if (!selector.startsWith("#")) {
            throw new RuntimeException("Unable to parse selector: '" + selector + "'.");
        }

        final String id = selector.substring(1);

        F<Tree<XmlNode>, Boolean> f;
        f = new F<Tree<XmlNode>, Boolean>() {
            public Boolean f(Tree<XmlNode> tree) {
                System.out.println("tree.root().getClass() = " + tree.root().getClass());
                if (!(tree.root() instanceof XmlElement)) {
                    return false;
                }
                XmlElement element = (XmlElement) tree.root();
                Option<String> idOption = element.attributes.get("id");
                Show.optionShow(Show.stringShow).println(idOption);
                return idOption.isSome() && idOption.some().equals(id);
            }
        };

//        Option<TreeZipper<XmlNode>> child = document.tree.findChild(f);

        Option<Tree<XmlNode>> child = findChild(document.tree, f);

        return new JQuery(document, child);
    }

    private Option<Tree<XmlNode>> findChild(Tree<XmlNode> zipper, F<Tree<XmlNode>, Boolean> f) {
        for (Tree<XmlNode> current : zipper.subForest()) {
            if(f.f(current)) {
                return some(current);
            }

            Option<Tree<XmlNode>> zipperOption = findChild(current, f);
            if(zipperOption.isSome()) {
                return zipperOption;
            }
        }

        return Option.none();
    }

    public String text() {
        StringBuilder text = new StringBuilder();

        for (Tree<XmlNode> match : matches) {
            text.append(match.root().getTextContent());
        }

        return text.toString();
    }

    // -----------------------------------------------------------------------
    //
    // -----------------------------------------------------------------------

    public static JQuery $(Document document) {
        return new JQuery(XmlTree.fromDocument(document), List.<Tree<XmlNode>>nil());
    }
}