org.json.JSONObject cannot be cast to java.util.Map

Question

Casting Map to a JSONObject for android app. Builds but crashes on run-time. Looked in the Logcat and got error:

org.json.JSONObject cannot be cast to java.util.Map

Here is the section related:

JSONObject item = new JSONObject(data);
Map product = ((Map)item.get("product"));

It's specifically the second line that's making it crash. I commented out code until un-commenting this line caused the crash.

The JSON it's linked to is here.

Unmapping the JSONObject gives this error:

Incompatible types.

Required: java.util.Map<, >

Found: java.lang.Object

More extensive code view:

        TextView parsed = findViewById(R.id.jsonParse);
        String barcodeNum = result.getText();
        String productName = "";

        try {
            URL url = new URL("https://world.openfoodfacts.org/api/v0/product/" + barcodeNum + ".json");
            HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
            InputStream inputStream = httpURLConnection.getInputStream();
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
            String data = "";
            String line = "";

            while (line != null){
                line = bufferedReader.readLine();
                data = data + line;
            }


            JSONObject item = new JSONObject(data);
            final JSONObject product = item.getJSONObject("product");
            final Map<String, Object> map =
                    product.keySet()
                            .stream()
                            .collect(Collectors.toMap(
                                    Function.identity(),
                                    product::get
                            ));

What is data and why Map? @George Hanlon

MS90
– MS90

2019-03-29 22:12:32 +00:00
Commented Mar 29, 2019 at 22:12 — MS90
– MS90, Commented Mar 29, 2019 at 22:12
@MS90 data is a parsed String of the json contents.

George Hanlon
– George Hanlon

2019-03-29 22:16:11 +00:00
Commented Mar 29, 2019 at 22:16 — George Hanlon
– George Hanlon, Commented Mar 29, 2019 at 22:16

LppEdd · Accepted Answer · 2019-03-29 23:05:13Z

2

JSONObject#get

isn't going to return a Map. Instead it will return another JSONObject, which describes the nested product property.

You'll see, indeed, it can be casted to it

final JSONObject product = (JSONObject) item.get("product");

What you can do is

final JSONObject product = item.getJSONObject("product");
final Map<String, Object> objectMap = product.toMap();

On old versions of JSON-Java, which don't offer the toMap method, what you can do is

final JSONObject product = item.getJSONObject("product");
final Map<String, Object> map =
        product.keySet()
               .stream()
               .collect(Collectors.toMap(
                       Function.identity(),
                       product::get
               ));

edited Mar 29, 2019 at 23:05

answered Mar 29, 2019 at 22:19

LppEdd

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21 Comments

George Hanlon Over a year ago

Thanks for this. Think I'm being stupid here but using .toMap() gives me: Cannot resolve method 'toMap()' Tried looking here: stackoverflow.com/questions/27841225/…

LppEdd Over a year ago

@GeorgeHanlon could you tell me which version of JSON-Java you're using? The toMap method is pretty recent, and you might not be able to use it on old releases.

LppEdd Over a year ago

@GeorgeHanlon updated with a way to obtain a Map when using old versions of JSON-Java.

George Hanlon Over a year ago

hm that's strange, the old version of JSON-Java method " Cannot resolve symbol 'jsonObject' ". Same with .keySet(). And yet it doesn't seem to have the .toMap() method. Apologies for being a novice, but how would I check the version of JSON-Java? Thanks for the help - really appreciated.

LppEdd Over a year ago

@GeorgeHanlon can you do a screenshot of the available methods?

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