String (Span span, boolean isStart) { StringBuilder sb = new StringBuilder(); sb.append("{\"name\": \"") .append(span.name) .append("\", \"cat\": \"PERF\", \"ph\": "); if (isStart) { sb.append("\"B\""); } else { sb.append("\"E\""); } sb.append(", \"pid\": ").append(pid) .append(", \"tid\": ").append(span.threadId) .append(", \"ts\": "); if (isStart) { sb.append(getTimeUs(span.startTimeNs)); } else { sb.append(getTimeUs(span.finishTimeNs)); } return sb.append("},\n").toString(); }