forEach will iterate over children of a JsonNode (converted to String when printed) and fieldNames() gets an Iterator<String> over keys. Here are some examples for printing elements of the example JSON:

JsonNode rootNode = mapper.readTree(option);

System.out.println("\nchoices:");
rootNode.path("choices").forEach(System.out::println);

System.out.println("\nAllKeys:");
rootNode.fieldNames().forEachRemaining(System.out::println);

System.out.println("\nChoiceSettings:");
rootNode.path("choiceSettings").fieldNames().forEachRemaining(System.out::println);

You'll probably need fields() at some point that returns an Iterator<Entry<String, JsonNode>> so you can iterate over key, value pairs.

You can use elements() method and check if value key exist then add the value to list.

Smaple code

ObjectMapper mapper = new ObjectMapper();
JsonNode jsonNode = mapper.readTree(data);

List<String> values = new ArrayList<>();
jsonNode.forEach(jsonObject -> jsonObject.elements().forEachRemaining(valueNode -> {
    if(valueNode.has("value"))
        values.add(valueNode.get("value").asText());
}));
System.out.println(values);

Output:

[http://www.wikidata.org/entity/Q42442324, http://www.wikidata.org/prop/direct/P21, Kiisu Miisu, http://www.wikidata.org/entity/Q43260736, http://www.wikidata.org/prop/direct/P21, Paddles]

For Jackson 2+ (com.fasterxml.jackson), the methods are little bit different:

CopyIterator<Entry<String, JsonNode>> nodes = rootNode.get("foo").fields();

while (nodes.hasNext()) {
  Map.Entry<String, JsonNode> entry = (Map.Entry<String, JsonNode>) nodes.next();

  logger.info("key --> " + entry.getKey() + " value-->" + entry.getValue());
}

To get the values of "last" using your approach, try this fragment:

Dim result As JsonObject = jsonResponse("result").AsObject

For Each kvp In result.AsEnumerable
    c &= kvp.Value("last").ToString & ", "
Next

You should treat the Value of you json object as a new JSONObject, which is already the case. Or more, the value in your case is an array of Json Objects.

So you can use:

JSONObject jsonObj = new JSONObject(field.getValue());

Or if you are not sure if it's an array or an object, please take a look on this link.

You can do something like this, iterate over the root node to get the required key fields ('1/1/0' and '1/1/1') and data for each object through the nested while loop and for-loop respectively.

final JsonNode node = parser.parseToNode(configJson); 

for (JsonNode root : node) {

            Iterator<String> itr = root.getFieldNames();
                while (itr.hasNext()) {  //to get the key fields
                String key_field = itr.next();
                }

            for (JsonNode n : node.get("sensors")) {  //to get each object
                final String event = root.get("event").asText();
                final String name = root.get("name").asText();
                final String type = root.get("type").asText();
                final String location = root.get("location").asText();
                }
   }

It would be easier if you have a pojo class mapped with your json to perform these operations when you are using jackson library.

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

With Jackson's tree model (JsonNode), you have both "literal" accessor methods (get), which returns null for missing value, and "safe" accessors (path), which allow you to traverse "missing" nodes. So, for example:

JsonNode root = mapper.readTree(inputSource);
int h = root.path("response").path("history").getValueAsInt();

which would return the value at the given path, or, if the path is missing, 0 (default value).

But more conveniently, you can just use JSON pointer expression:

int h = root.at("/response/history").getValueAsInt();

There are other ways too, and often it is more convenient to model your structure as a Plain Old Java Object (POJO). Your content could fit something like:

public class Wrapper {
  public Response response;
} 
public class Response {
  public Map<String,Integer> features; // or maybe Map<String,Object>
  public List<HistoryItem> history;
}
public class HistoryItem {
  public MyDate date; // or just Map<String,String>
  // ... and so forth
}

and if so, you would traverse the resulting objects just like any Java object.