How to check the type of a value from a JSONObject?

The best solution is to use JSONObject.get() and check for the type using instanceof operator.

You can get the object from the JSON with the help of JSONObject.get() method and then using the instanceof operator to check for the type of Object.

Something on these lines:-

String jString = "{\"a\": 1, \"b\": \"str\"}";
JSONObject jObj = new JSONObject(jString);
Object aObj = jObj.get("a");
if (aObj instanceof Integer) {
    // do what you want
}

Please note that JSONObject.get() may return an integer as either java.lang.Integer or java.lang.Long, for example, for {a:3,b:100300000000} we see

D/+++     ( 5526): +++a=>class java.lang.Integer:3
D/+++     ( 5526): +++b=>class java.lang.Long:100300000000

I use the code like (note that we use types long and double instead of int and float, and that in my task there may be no nested JSONObject or JSONArray so they are not supported):

    for (String k : new AsIterable<String>(json.keys())) {
            try {
                    Object v = json.get(k);
        //Log.d("+++","+++"+k+"=>"+v.getClass()+":"+v);
                    if (v instanceof Integer || v instanceof Long) {
                            long intToUse = ((Number)v).longValue();
                            ...
                    } else if (v instanceof Boolean) {
                            boolean boolToUse = (Boolean)v).booleanValue();
                            ...
                    } else if (v instanceof Float || v instanceof Double) {
                            double floatToUse = ((Number)v).doubleValue();
                            ...
                    } else if (JSONObject.NULL.equals(v)) {
                            Object nullToUse = null;
                            ...
                    } else {
                            String stringToUse = json.getString(k);
                            ...
                    }
            } catch (JSONException e2) {
                    // TODO Auto-generated catch block
                    Log.d("exc: "+e2);
                    e2.printStackTrace();
            }
    }

where AsIterable lets us use the for(:) loop with an iterator and is defined as:

public class AsIterable<T> implements Iterable<T> {
    private Iterator<T> iterator;
    public AsIterable(Iterator<T> iterator) {
        this.iterator = iterator;
    }
    public Iterator<T> iterator() {
        return iterator;
    }
}