replace simple factory using polymorfism

Hy guys,

I'll tring to replace the simple factory StatsCreatorFactory.java class in order to delete the stink multiple use of switch case statements. This is my situation:

StatsServlet.java

public class StatsServlet extends HttpServlet{ 

    private static final long serialVersionUID = 1L;

    protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        StatsContext context = new StatsContext(request,response);
        **IStatsCreator creator = StatsCreatorFactory.getCreator(context);**
        IChart chart = creator.createChart();
        String jsonChart = creator.chartToJson(chart);
        creator.sendResponse(jsonChart);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        processRequest(request, response);
    }

}

IStatsCreator.java

public interface IStatsCreator {

    public IChart createChart() throws IOException;
    public  IDetailsTable createDetailsTable(String itemSelected);

    public String chartToJson(IChart chart);
    public String tableToJson(IDetailsTable table);

    public void sendResponse(String resp) throws IOException;


    public List<File> findFiles() throws IOException, ParseException;
    public List<LogLine> parseFiles(List<File> files) throws IOException;
    public IFileIntervalDateDetector getFileDetector() throws IOException;

    public TargetChartOperation getTargetOperation();
    public IChart getChart();
    public IDetailsTable getDetailsTable();
}

AbstractStatsCreator

public abstract class AbstractStatsCreator implements IStatsCreator{

    protected StatsContext context;

    public AbstractStatsCreator(StatsContext context) {
        this.context = context;
    }

    protected abstract ILogParser getParser();
    protected abstract IStatsHelper getHelper();

    @Override
    public IFileIntervalDateDetector getFileDetector() throws IOException {
        IFileIntervalDateDetector fileDetector = new FileDetector();
        fileDetector.addPattern(new FileNamePattern(TypeSubjectEnum.valueOf(context.getSubject().toUpperCase()).getFilePattern()));
        fileDetector.addPattern(new FileNamePattern(context.getInstance()));
        return fileDetector;
    }

    @Override
    public final List<File> findFiles() throws IOException, ParseException{
        if(context.getDateStart().equalsIgnoreCase(StringUtils.EMPTY) && context.getDateEnd().equalsIgnoreCase(StringUtils.EMPTY)){
            return getFileDetector().findDailyFiles();
        }

        Date startDate = new SimpleDateFormat("ddMMyyyy").parse(context.getDateStart());
        Date stopDate = new SimpleDateFormat("ddMMyyyy").parse(context.getDateEnd());
        Date currentDate = new Date(System.currentTimeMillis());

        if(DateUtils.isSameDay(startDate, stopDate) && DateUtils.isSameDay(startDate, currentDate)){
            return getFileDetector().findDailyFiles();
        }

        return getFileDetector().findFilesByInterval(context.getDateStart(), context.getDateEnd()); 
    }

    @Override
    public final List<LogLine> parseFiles(List<File> files) throws IOException{
        return getParser().parseLogFiles(files);
    }

    @Override
    public IChart createChart() throws IOException{

        if(context.needUpdate()){
            List<File> files = null;
            try {
                files = findFiles();
            } catch (ParseException e) {
                files=Lists.newArrayList();
            }
            List<LogLine> logLines = parseFiles(files);
            context.setLogLines(logLines);
            context.updateContext(); 
        }

        IChart chart = getChart().create();
        return chart;
    }

    @Override
    public IDetailsTable createDetailsTable(String itemSelected) {
        IDetailsTable table = getDetailsTable().create(itemSelected);
        return table;
    }

    @Override
    public String chartToJson(IChart chart) {
        StringBuilder json = new StringBuilder(JsonTransformer.renderChart(chart));
        return json.toString();
    }

    @Override
    public String tableToJson(IDetailsTable table) {
        StringBuilder json = new StringBuilder(JsonTransformer.renderDetailsTable(table));
        return json.toString();
    }

    @Override
    public void sendResponse(String resp) throws IOException {
        context.getResponse().setContentType("application/json");
        PrintWriter out = context.getResponse().getWriter();
        out.write(resp.toString());
        out.flush();
    }

}

StatsCreatorFactory.java

public class StatsCreatorFactory {

    public static IStatsCreator getCreator(StatsContext context){

        if(context == null){
            throw new IllegalArgumentException("Context nullo");
        }

        IStatsCreator creator=null;

        switch (context.getOperation()) {
        case "validate":
            creator = new ValidateStatsCreator(context);
            break;
        case "extract":
            creator = new ExtractStatsCreator(context);
            break;
        case "transform":
            creator = new TransformStatsCreator(context);
            break;
        case "view":
            creator = new ViewStatsCreator(context);
            break;  
        default:
            creator = new GeneralStatsCreator(context);
            break;
        }

        return creator;
    }
}

I would try to find a way to instanciate ICreator classes avoiding simple factory class, is there any refactoring or design pattern could I use? Reading Martin Fawler book's I wondering if I can use polymorfism, but I can't any way to applicate it in my code. Thanks in advance.