public void addContentSize(final long contentSize) {
        this.contentSize += contentSize;
    }

    public long getProcessingTime() {
        return processingTime;
    }

    public void addProcessingTime(final long processingTime) {
        this.processingTime += processingTime;
    }

    @Override
    public String toString() {

        DocList docList = new DocList();

        assertEquals(0, docList.getContentSize());
        assertEquals(0, docList.getProcessingTime());

        docList.addContentSize(1000);
        docList.addProcessingTime(999);
        assertEquals(1000, docList.getContentSize());
        assertEquals(999, docList.getProcessingTime());

        docList.clear();
        assertEquals(0, docList.getContentSize());

            docList.addContentSize(contentSize);
            final long processingTime = systemHelper.getCurrentTimeAsLong() - startTime;
            docList.addProcessingTime(processingTime);
            if (logger.isDebugEnabled()) {
                logger.debug("Added the document({}, {}ms). The number of a document cache is {}.",

                    docList.addContentSize(contentSize);
                    final long processingTime = systemHelper.getCurrentTimeAsLong() - startTime;
                    docList.addProcessingTime(processingTime);
                    if (logger.isDebugEnabled()) {
                        logger.debug("Added the document({}, {}ms). The number of a document cache is {} (size: {}).",