json按key进行排序ASCII

private static String recursiveKeySort(JsonObject json) {
        StringBuilder appender = new StringBuilder();
        appender.append("{");
        Iterator<String> keys = new TreeSet<>(json.keySet()).iterator();
        boolean isFirstEle = true;
        while (keys.hasNext()) {
            if (!isFirstEle) {
                appender.append(",");
            }
            String key = keys.next();
            Object val = json.get(key);
            if (val instanceof JsonObject) {
                appender.append("\"").append(key).append("\":");
                appender.append(recursiveKeySort((JsonObject)val));
            } else if (val instanceof JsonArray) {
                JsonArray jarray = (JsonArray)val;
                appender.append("\"").append(key).append("\":[");
                boolean isFirstArrEle = true;
                for (int i = 0; i < jarray.size(); i++) {
                    if (!isFirstArrEle) {
                        appender.append(",");
                    }
                    Object obj = jarray.get(i);
                    if (obj instanceof JsonObject) {
                        appender.append(recursiveKeySort((JsonObject)obj));
                    } else {
                        appender.append(obj.toString());
                    }
                    isFirstArrEle = false;
                }
                appender.append("]");
            } else {
                String value = val.toString();
                appender.append("\"").append(key).append("\":").append(value);
            }
            isFirstEle = false;
        }
        appender.append("}");
        return appender.toString();
    }