Null condition check not working in parsing JSON array with nested objects

Beginner in Java working on parsing JSON array with nested objects into simplified JSON array using the below code.

It works fine if there are no null values in the object. The null value check appears to be faulty. I've tried other ways like ==null or equals(null) or equals("null") or !=null or !="null" or =="null" as well before this.

import com.google.gson.*;

public class DataParser {
    public static JsonArray parseData(JsonArray data) throws JsonParseException {
		JsonArray dataArray = new JsonArray();
    	for (Object dataObj : data) {
            JsonParser parser = new JsonParser();
            JsonObject obj = (JsonObject) parser.parse(dataObj.toString());
            JsonObject finalDataObj = new JsonObject();            
            Object fields = obj.get("fields");            
            JsonObject fieldsObj = (JsonObject) parser.parse(fields.toString());
			finalDataObj.add("key", obj.get("key"));
            finalIssueObj.addProperty("cityName", displayName(fieldsObj.get("cityName")));
            finalIssueObj.addProperty("category", displayName(fieldsObj.get("category")));
    		dataArray.add(finalDataObj);
    	}
		return dataArray;
    }
	
	 public static String displayName(Object dataValue){
        if ( dataValue == null){
             return "";
        }
        else {            
            JsonObject obj = (JsonObject)dataValue;
            return obj.get("name").toString();
        }
    }	
}

Input:

[{"key":"1232", "fields": {cityName":{"id":"10000","description":"This is city name","iconUrl":"https://iconurls.com","name":"Hyderabad","subtask":false},"updated":"2023-05-31","category":{"description":"This is category of city.","iconUrl":"https://category1.icon.com","name":"Dining"}}},
{"key":"1233", "fields": {cityName":null,"updated":"2023-05-31","category":null}}]

Output:

[{"key" : "1232", "cityName": "Hyderabad", "category" : "Dining"}, 
{"key" : "1233", "cityName": "", "category" : ""} ]`

In the provided code, you are trying to check for null values using dataValue == null. However, in the case of JSON objects, checking for null using == won't work as expected. Instead, you can use the JsonNull class provided by the Gson library to check for null values.

public static String displayName(JsonElement dataValue) {
   if (dataValue == null || dataValue.isJsonNull()) {
       return "";
   } else {
       JsonObject obj = dataValue.getAsJsonObject();
       return obj.get("name").getAsString();
   }
}

Additionally, dataObj in the parseData method is of type JsonElement instead of Object to avoid unnecessary conversions.

    for (JsonElement dataObj : data) {
       JsonParser parser = new JsonParser();
       JsonObject obj = dataObj.getAsJsonObject();
       JsonObject finalDataObj = new JsonObject();

       JsonObject fieldsObj = obj.getAsJsonObject("fields");
       finalDataObj.add("key", obj.get("key"));
       finalDataObj.addProperty("cityName", displayName(fieldsObj.get("cityName")));
       finalDataObj.addProperty("category", displayName(fieldsObj.get("category")));

       dataArray.add(finalDataObj);
    }