public FileResourceCrawlerFutureResult call() {
        try {
            start();
        } catch (InterruptedException e) {
            //this can be triggered by shutdownNow in BatchProcess
            LOG.info("InterruptedException in FileCrawler", e);
        } catch (Exception e) {
            LOG.error("Exception in FileResourceCrawler: {}", e.getMessage(), e);
        } finally {
            isActive = false;
        }

        try {
            shutdown();
        } catch (InterruptedException e) {
            //swallow
        }

        return new FileResourceCrawlerFutureResult(considered, added);
    }
Implement this to control the addition of FileResources.  Call {@link #tryToAdd}
to add FileResources to the queue.

@throws InterruptedException
tika-batch/src/main/java/org/apache/tika/batch/FileResourceCrawler.java