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

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 getAllKeys(JSONObject json) {
    return getAllKeys(json, new HashSet<>());
}

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

private static Set getAllKeys(JSONArray arr, Set 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 getAllKeys(JSONObject json, Set 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;
}