Problem
The constructors org.json.JSONObject.JSONObject(Map<?, ?>) and org.json.JSONObject.JSONObject(Object) do not check occuring numbers in values for finiteness and thus allow creating of invalid JSON object which then run into strange behaviour when stringifying.

The Map constructor even mentiones @throws JSONException - If a value in the map is non-finite number. but this exception can only occur here when a nested call throws it, e.g. a value with a List containing non-finite numbers.

Code example

import static org.junit.jupiter.api.Assertions.assertThrows;
import java.util.Map;
import org.json.JSONException;
import org.json.JSONObject;
import org.junit.jupiter.api.Test;

class JSONObjectTest {
    @Test void jsonObject_map() {
        assertThrows(JSONException.class, () -> new JSONObject(Map.of("a", Double.POSITIVE_INFINITY)));
    }

    @Test void jsonObject_bean() {
        assertThrows(JSONException.class, () -> new JSONObject(new MyBean()));
    }
    public static class MyBean {
        public double getA() { return Double.POSITIVE_INFINITY; }
    }
}

Both tests fail and instead the constructors return an instance of a JSONObject with a key "a" mapped to a non-finite double.

Cascading problems
Calling toString() on the returned JSONObject will internally throw a JSONException in toString(0) while writing the non-finite value and this will be catched resulting in a null returned from the method. obj.getDouble("a") on the other hand will return the non-finite double.

Idea
While JSONObject.put(String, Object) checks for finiteness before putting the value to the map

the other two calls

just wrap() the value so it might be a good idea to do the finiteness-check there and document the JSONException.