Trading Engine Servlet, using threads

TreadingEngineServlet-threads.java

@WebServlet(urlPatterns = { "/sell", "/buy", "/result" })
public class TradingEngineServlet extends HttpServlet {
    private static final Map<String, TradingEngineThread> kids = new HashMap<>();
    static {
        int chunk = PRODUCT_IDS.length / NUM_KIDS;
        for (int i = 0, j = PRODUCT_IDS.length; i < j; i += chunk) {
            String[] temparray = Arrays.copyOfRange(PRODUCT_IDS, i, i + chunk);
            LOGGER.info("created engine for products " + temparray);
            TradingEngineThread engineThread = new TradingEngineThread(DELAY, TIMEOUT, (type, data) -> event(type, data));
            for (int k = 0; k < temparray.length; k++) {
                LOGGER.debug("mapping productId '" + temparray[k] + "' to engine " + i);
                kids.put(temparray[k], engineThread);
            }
            LOGGER.info("---started trading");
            engineThread.start();
        }