If you're trying to find a key which is placed inside nested object, you may use findValue(String key) method which returns null if a value is not found by the given key:

ObjectMapper mapper = new ObjectMapper();
JsonNode rootNode= mapper.readTree(json);

String[] keys = {
    "id", "create_date", "versions_control_advanced", "name", "nofield"
};

for (String key : keys) {
    JsonNode value = rootNode.findValue(key);
    System.out.printf("Key %s exists? %s --> value=%s%n", key, value != null,
                    value == null ? null : value.asText());

}

Output:

Key id exists? true --> value=276625
Key create_date exists? true --> value=2020-06-22T16:19:07
Key versions_control_advanced exists? true --> value=false
Key name exists? true --> value=
Key nofield exists? false --> value=null

JSONObject class has a method named "has":

http://developer.android.com/reference/org/json/JSONObject.html#has(java.lang.String)

Returns true if this object has a mapping for name. The mapping may be NULL.

To do a proper null check of a JsonNode field:

JsonNode jsonNode = response.get("item");

if(jsonNode == null || jsonNode.isNull()) { }

The item is either not present in response, or explicitly set to null .

Use below code to find key is exist or not in JsonObject. has("key") method is used to find keys in JsonObject.

containerObject = new JSONObject(container);
//has method
if (containerObject.has("video")) {
    //get Value of video
    String video = containerObject.optString("video");
}

If you are using optString("key") method to get String value then don't worry about keys are existing or not in the JsonObject.

You just get Response object from your call and do:

public class Test {

    public static void main(String[] args) {
        Response response = RestAssured
                .get("https://mocki.io/v1/22617277-2eca-4fcf-b7e2-8c80851ef45d");
        if(response.path("shop.type") == null){
            System.out.println("key does not exist");
        }else{
            System.out.println(response.path("shop.type").toString());
        }
    }

}

You can have more complicated jsonpath query. For example if you treat having field with null value in different way than having no field at all you can use find in your jsonpath like I'm showing below:

if(response.path("shop.find{it.getKey() == 'type'}") != null){
    System.out.print("Key exists ");
    if(response.path("shop.type") == null){
        System.out.println("but have null value");
    }else{
        System.out.println("and have not-null value");
    }
}else{
    System.out.println("Key does not exist");
}

You can use JSONObject to parse your json and use its has(String key) method to check wether a key exists in this Json or not:

 String str="{\"claim_loss_type_cd\": \"TEL\",\"claim_type\":\"002\",\"claim_reason\": \"001\",\"policy_number\":\"1234kk3366ff664\",\"info\": {\"ApplicationContext\":{\"country\": \"US\"}}}";
 Object obj=JSONValue.parse(str);
 JSONObject json = (JSONObject) obj;
 //Then use has method to check if this key exists or not
 System.out.println(json.has("claim_type")); //Returns true

EDIT:

Or better you can simply check if the JSON String contains this key value, for example with indexOf() method:

String str="{\"claim_loss_type_cd\": \"TEL\",\"claim_type\":\"002\",\"claim_reason\": \"001\",\"policy_number\":\"1234kk3366ff664\",\"info\": {\"ApplicationContext\":{\"country\": \"US\"}}}";
System.out.println(str.indexOf("claim_type")>-1); //Returns true

EDIT 2:

Take a look at this method, it iterates over the nested objects to check if the key exists.

public boolean keyExists(JSONObject  object, String searchedKey) {
    boolean exists = object.has(searchedKey);
    if(!exists) {      
        Iterator<?> keys = object.keys();
        while( keys.hasNext() ) {
            String key = (String)keys.next();
            if ( object.get(key) instanceof JSONObject ) {
                    exists = keyExists(object.get(key), searchedKey);
            }
        }
    }
    return exists;
}

Object obj=JSONValue.parse(str);
JSONObject json = (JSONObject) obj;
System.out.println(keyExists(json, "country")); //Returns true