List<Map<String,String>>

StringBuilder sb = new StringBuilder();
        sb.append("{");
   for(Map<String,String> map:list){
        for (String key : map.keySet()) {
            sb.append("\"").append(key).append("\":\"").append(map.get(key))
                    .append("\"").append(",");
        }
}
        sb.deleteCharAt(sb.lastIndexOf(","));
        sb.append("}");