public void notifyPageCrawled(Page page) {
        this.pageCrawledEvent(page);
        int numberOfPages = this.pageCounter.incrementAndGet();
        if (numberOfPages % learnLimit == 0) {
            if (this.async) {
                doNotify(); // triggers execution of online learning in background thread
            } else {
                executeLearning();
            }
        }
        numberOfPages++;
    }
Pauses online learning thread until {@link #doNotify()} is called.
ache/src/main/java/achecrawler/link/classifier/online/OnlineLearning.java