final StringBuilder b = new StringBuilder();
            b.append('"').append(StringEscapeUtils.escapeJson(c.getName())).append("\":{");
            append(b, "count", () -> c.getCollectionCount()).append(',');
            append(b, "time", () -> c.getCollectionTime().getMillis()).append('}');
            return b.toString();
        }).collect(Collectors.joining(",")));
        buf.append("},");