1I use Gson class in order to convert a
2Json object into a java object.
3If it works without any error, it means that it is a valid json format...
4
5import com.google.gson.Gson;
6
7public class JSONUtils {
8
9  Gson gson = new Gson();
10
11  public boolean isJSONValid(String jsonInString) {
12      try {
13          gson.fromJson(jsonInString, Object.class);   
14          return true;
15      } catch(com.google.gson.JsonSyntaxException e) { 
16          return false;
17      }
18  }
19}

1//extensive check to make sure object is not of string type and not null
2function isJson(item) {
3    item = typeof item !== "string"
4        ? JSON.stringify(item)
5        : item;
6
7    try {
8        item = JSON.parse(item);
9    } catch (e) {
10        return false;
11    }
12
13    if (typeof item === "object" && item !== null) {
14        return true;
15    }
16
17    return false;
18}