How to get all keys from a JSON-Object as a String array in Java

Question

I have a JSON Object which I created from a .json file which looks like the follownig:

{
  "key1": {
    "key2": "value2",
    "key3": "value3",
  }
}

To generate the JSON-Object I use:

JSONObject newJSON = new JSONObject(content);

What I want to do, is to generate a String array, which contains all keys of the existing JSONObject, to easily access them.

Please also provide information on what you have tried so far and what did not work about this, please see: stackoverflow.com/help/how-to-ask — Sven Hakvoort
– Sven Hakvoort, Commented Oct 15, 2018 at 10:44

Lie Ryan · Accepted Answer · 2018-10-15 11:01:47Z

3

JSONObject implements the Map interface, so you can use the same way you'd use for Map to generate the list of keys. In particular, you can use the .keySet() or .entrySet() method.

For example (adapted from here):

JSONObject jsonObj = ...;
List<String> l = new ArrayList<String>(jsonObj.keySet());

edited Oct 15, 2018 at 11:01

answered Oct 15, 2018 at 10:48

Lie Ryan

65.3k14 gold badges103 silver badges151 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Donald Duck is with Ukraine Over a year ago

This answer is incorrect. jsonObj.keySet() gives me an error "Cannot resolve method 'keySet' in 'JSONObject'".

Ramesh Yankati · Accepted Answer · 2018-10-15 10:49:53Z

1

         You could iterate through the keys.
          JSONObject newUserJSON = new JSONObject(content);
          ArrayList<String> keys = new ArrayList<>();
          String key;

          for (Iterator<String> it = newUserJSON.keys(); it.hasNext(); ) {
             key = it.next();
             keys.add(key);
           }
      And also you need to take care of nested json Object for each key.

answered Oct 15, 2018 at 10:49

Ramesh Yankati

1,2179 silver badges15 bronze badges

Comments

Piotr Wittchen · Accepted Answer · 2018-10-15 10:51:54Z

1

Answer to this question is already available in another SO thread: Convert string to JSON array

Here's the equivalent for your use case:

JSONObject jsnobject = new JSONObject(content);

JSONArray jsonArray = jsnobject.getJSONArray("key1");
for (int i = 0; i < jsonArray.length(); i++) {
    JSONObject explrObject = jsonArray.getJSONObject(i);
}

answered Oct 15, 2018 at 10:51

Piotr Wittchen

3,9224 gold badges29 silver badges44 bronze badges

Collectives™ on Stack Overflow

How to get all keys from a JSON-Object as a String array in Java

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related