Extracting Keys from a JSONObject using keySet()

Question

I\'m trying to extract the keys from a JSON Object. The JSON object, in this case, is obtained by making an API call to a social networking site called SkyRock and

Answer 1

My JSONOject is jsonOject;

  Iterator <String> listKEY = jsonOject.keys();
                do {
              String newKEY = listKEY.next().toString();
                   
                }while (listKEY.hasNext());

Answer 2

This works for me

o is a JSONObject -> import org.json.simple.JSONObject;

Set<?> s =  o.keySet();

    Iterator<?> i = s.iterator();
    do{
        String k = i.next().toString();
        System.out.println(k);

    }while(i.hasNext());

Answer 3

The posts represents Map of JSONObject where key is String

JSONObject mainObject = new JSONObject(jsonString);

JSONObject posts = mainObject.getJSONObject("posts");

Map<String, JSONObject> map = (Map<String,JSONObject>)posts.getMap();

ArrayList<String> list = new ArrayList<String>(map.keySet());

System.out.println(list);

Output:

[3116902311, 3114564209, 3111623007]

Answer 4

Recursive methods for extracting keys from json objects and arrays (in case of duplicates will merge them since methods return Set, but not Array)

public static Set<String> getAllKeys(JSONObject json) {
    return getAllKeys(json, new HashSet<>());
}

public static Set<String> getAllKeys(JSONArray arr) {
    return getAllKeys(arr, new HashSet<>());
}

private static Set<String> getAllKeys(JSONArray arr, Set<String> keys) {
    for (int i = 0; i < arr.length(); i++) {
        Object obj = arr.get(i);
        if (obj instanceof JSONObject) keys.addAll(getAllKeys(arr.getJSONObject(i)));
        if (obj instanceof JSONArray) keys.addAll(getAllKeys(arr.getJSONArray(i)));
    }

    return keys;
}

private static Set<String> getAllKeys(JSONObject json, Set<String> keys) {
    for (String key : json.keySet()) {
        Object obj = json.get(key);
        if (obj instanceof JSONObject) keys.addAll(getAllKeys(json.getJSONObject(key)));
        if (obj instanceof JSONArray) keys.addAll(getAllKeys(json.getJSONArray(key)));
    }

    keys.addAll(json.keySet());
    return keys;
}

Answer 5

The javadoc says:

public interface JsonObject
extends JsonStructure, Map<String,JsonValue>

So, a JSONObject is a Map whose keys are of type String, and whose values are of type JSONValue.

And the javadoc of Map<K, V>.keySet() says:

Set<K> keySet()

Returns a Set view of the keys contained in this map

So, what JSONObject.keySet() returns is a Set<String> (which is quite logical, since keys of JSON objects are strings).

So all that you want is:

Set<String> keys = posts.keySet();