testing AST nodes

In SimpleNode, there is a protected field (id) that I wish to use to
compare against the
constants generated on the XXXTreeConstants interface

Right now I have to do: ...

public class MyVisitor implements XXXVisitor {

    public Object visit(ASTDeclarativeSection node, Object data)
throws Exception {
        ArrayList<Node> types = new ArrayList<Node>();
        ArrayList<Node> programUnits = new ArrayList<Node>();
        for (int i=0; i < node.jjtGetNumChildren(); i++ ) {
            Node n = node.jjtGetChild(i);
            if (n instanceof ASTProgramUnit) {
                programUnits.add(n);
            }
            else if (n instanceof ASTTypeDefinition) {
                types.add(n);
            }
        }
        // visit types before programUnits
        for (int i=0; i < types.size(); i++ ) {
            Node n = types.get(i);
            n.jjtAccept(this, data);
        }
        for (int i=0; i < programUnits.size(); i++ ) {
            Node n = programUnits.get(i);
            Object o = n.jjtAccept(this, data);
        }
        return data;
    }

It would be a lot nicer if one could do something like:

            if (n.getId() == XXXTreeConstants.JJTPROGRAMUNIT) {
                programUnits.add(n);
            }
            else if (n.getId() == XXXTreeConstants.JJTTYPEDEFINITION)
{
                types.add(n);
            }

instead of the instanceof check